Orthogonal frequency division multiple access for wireless local area network

ABSTRACT

A plurality of different OFDM tone blocks for a wireless local area network (WLAN) communication channel are assigned to a plurality of devices. An OFDMA data unit is generated, the OFDMA unit including a preamble portion and a data portion, the preamble portion having at least i) a first legacy portion that corresponds to at least a first OFDM tone block, ii) a second legacy portion that corresponds to a second OFDM tone block, iii) a first non-legacy portion that corresponds to the first OFDM tone block, iv) a second non-legacy portion that corresponds to the second OFDM tone block, and v) a third non-legacy portion that corresponds to a third OFDM tone block. The first OFDM tone block and the second OFDM tone block are separated in frequency by at least the third OFDM tone block.

CROSS-REFERENCES TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.14/955,017 (now U.S. patent Ser. No. 10/009,894), entitled “OrthogonalFrequency Divisional Multiple Access for Wireless Local Area Network,”filed Nov. 30, 2015, which is a divisional of U.S. patent applicationSer. No. 14/553,974 (now U.S. Pat. No. 9,717,086), entitled “OrthogonalFrequency Division Multiple Access for Wireless Local Area Network,”filed Nov. 25, 2014, which claims the benefit of U.S. Provisional PatentApplication No. 61/909,616, entitled “OFDMA for WLAN: PHY Formats,”filed on Nov. 27, 2013, and U.S. Provisional Patent Application No.61/987,778, entitled “Range Extension PHY,” filed on May 2, 2014. All ofthe patent applications referenced above are hereby incorporated byreference herein in their entireties.

FIELD OF THE DISCLOSURE

The present disclosure relates generally to communication networks and,more particularly, to wireless local area networks that utilizeorthogonal frequency division multiple access.

BACKGROUND

When operating in an infrastructure mode, wireless local area networks(WLANs) typically include an access point (AP) and one or more clientstations. WLANs have evolved rapidly over the past decade. Developmentof WLAN standards such as the Institute for Electrical and ElectronicsEngineers (IEEE) 802.11a, 802.11b, 802.11g, and 802.11n Standards hasimproved single-user peak data throughput. For example, the IEEE 802.11bStandard specifies a single-user peak throughput of 11 megabits persecond (Mbps), the IEEE 802.11a and 802.11g Standards specify asingle-user peak throughput of 54 Mbps, the IEEE 802.11n Standardspecifies a single-user peak throughput of 600 Mbps, and the IEEE802.11ac Standard specifies a single-user peak throughput in thegigabits per second (Gbps) range. Future standards promise to provideeven greater throughputs, such as throughputs in the tens of Gbps range.

SUMMARY

In an embodiment, a method for generating an orthogonal frequencydivision multiple access (OFDMA) data unit includes assigning aplurality of different orthogonal frequency division multiplex (OFDM)tone blocks for a wireless local area network (WLAN) communicationchannel to a plurality of devices including a first device and seconddevice. The plurality of different OFDM tone blocks includes at least afirst OFDM tone block assigned to the first device and a second OFDMtone block assigned to the second device. The first OFDM tone block andthe second OFDM tone block together span a bandwidth equal to a smallestchannel bandwidth of a legacy WLAN communication protocol. The methodalso includes generating an OFDMA data unit for the WLAN communicationchannel. The OFDMA unit including a preamble portion and a data portion.The preamble portion has i) at least a legacy portion that spans theentire WLAN communication channel, ii) a first non-legacy portion thatspans the first OFDM tone block, and iii) a second non-legacy portionthat spans the second OFDM tone block.

In another embodiment, an apparatus includes a network interface devicehaving one or more integrated circuits. The one or more integratedcircuits are configured to assign a plurality of different orthogonalfrequency division multiplex (OFDM) tone blocks for a wireless localarea network (WLAN) communication channel to a plurality of devicesincluding a first device and second device. The plurality of differentOFDM tone blocks includes at least a first OFDM tone block assigned tothe first device and a second OFDM tone block assigned to the seconddevice. The first OFDM tone block and the second OFDM tone blocktogether span a bandwidth equal to a smallest channel bandwidth of alegacy WLAN communication protocol. The one or more integrated circuitsare further configured to generate an orthogonal frequency divisionmultiple access (OFDMA) data unit for the WLAN communication channel,the OFDMA unit including a preamble portion and a data portion, thepreamble portion having i) at least a legacy portion that spans theentire WLAN communication channel, ii) a first non-legacy portion thatspans the first OFDM tone block, and iii) a second non-legacy portionthat spans the second OFDM tone block.

In yet another embodiment, a method for generating a portion of an OFDMAdata unit includes determining an assignment of a first orthogonalfrequency division multiplex (OFDM) tone block within a wireless localarea network (WLAN) communication channel. A bandwidth of the first OFDMtone block is less than a smallest bandwidth of a legacy WLANcommunication protocol. The method also includes generating, at a firstcommunication device, a first portion of an orthogonal frequencydivision multiple access (OFDMA) data unit for transmission on the WLANcommunication channel using data tones and pilot tones within the firstOFDM tone block.

In an embodiment, a first communication device includes a networkinterface device having one or more integrated circuits. The one or moreintegrated circuits are configured to determine an assignment of a firstorthogonal frequency division multiplex (OFDM) tone block within awireless local area network (WLAN) communication channel. A bandwidth ofthe first OFDM tone block is less than a smallest bandwidth of a legacyWLAN communication protocol. The one or more integrated circuits arefurther configured to generate, at a first communication device, a firstportion of an orthogonal frequency division multiple access (OFDMA) dataunit for transmission on the WLAN communication channel using data tonesand pilot tones within the first OFDM tone block.

In an embodiment, a method for generating an OFDMA data unit includesassigning a plurality of different OFDM tone blocks for a WLANcommunication channel to a plurality of devices including a first deviceand second device. The plurality of different OFDM tone blocks includesat least a first OFDM tone block and a second OFDM tone block assignedto the first device and a third OFDM tone block assigned to the seconddevice. The first OFDM tone block and the second OFDM tone block areseparated in frequency by at least the third OFDM tone block. The methodalso includes generating an OFDMA data unit for the WLAN communicationchannel. The OFDMA unit includes a preamble portion and a data portion.The preamble portion has at least i) a first legacy portion thatcorresponds to at least the first OFDM tone block, ii) a second legacyportion that corresponds to the second OFDM tone block, iii) a firstnon-legacy portion that corresponds to the first OFDM tone block, iv) asecond non-legacy portion that corresponds to the second OFDM toneblock, and v) a third non-legacy portion that corresponds to the thirdOFDM tone block. The first legacy portion is modulated on at least thefirst OFDM tone block. The first non-legacy portion is modulated on thefirst OFDM tone block. The second legacy portion is modulated on atleast the second OFDM tone block. The second non-legacy portion ismodulated on the second OFDM tone block. The third non-legacy portion ismodulated on the third OFDM tone block.

In another embodiment, an apparatus includes a network interface devicehaving one or more integrated circuits. The one or more integratedcircuits are configured to assign a plurality of different OFDM toneblocks for a WLAN communication channel to a plurality of devicesincluding a first device and second device. The plurality of differentOFDM tone blocks includes at least a first OFDM tone block and a secondOFDM tone block assigned to the first device and a third OFDM tone blockassigned to the second device. The first OFDM tone block and the secondOFDM tone block are separated in frequency by at least the third OFDMtone block. The one or more integrated circuits are also configured togenerate an OFDMA data unit for the WLAN communication channel. TheOFDMA unit includes a preamble portion and a data portion. The preambleportion has at least i) a first legacy portion that corresponds to atleast the first OFDM tone block, ii) a second legacy portion thatcorresponds to the second OFDM tone block, iii) a first non-legacyportion that corresponds to the first OFDM tone block, iv) a secondnon-legacy portion that corresponds to the second OFDM tone block, andv) a third non-legacy portion that corresponds to the third OFDM toneblock. The first legacy portion is modulated on at least the first OFDMtone block. The first non-legacy portion is modulated on the first OFDMtone block. The second legacy portion is modulated on at least thesecond OFDM tone block. The second non-legacy portion is modulated onthe second OFDM tone block. The third non-legacy portion is modulated onthe third OFDM tone block.

In yet another embodiment, a method for generating a portion of an OFDMAdata unit includes determining an assignment of a first OFDM tone blockand a second OFDM tone block for a WLAN communication channel. The firstOFDM tone block corresponds to a first fast Fourier transform (FFT) sizethat is less than an FFT size corresponding to the WLAN communicationchannel. The second OFDM tone block corresponds to a second FFT sizethat is less than the FFT size corresponding to the WLAN communicationchannel. The first OFDM tone block and the second OFDM tone block areseparated in frequency by at least a third OFDM tone block. The methodfurther includes generating, at a first communication device, a portionof an OFDMA data unit for transmission on the WLAN communication channelusing data tones and pilot tones within the first OFDM tone block andthe second OFDM tone block.

In an embodiment, a method for generating an OFDMA data unit includesassigning a plurality of different OFDM frequency sub-bands for a WLANcommunication channel to a plurality of devices including a first deviceand second device. The plurality of different OFDM frequency sub-bandsincludes at least a first OFDM frequency sub-band assigned to the firstdevice and a second OFDM frequency sub-band assigned to the seconddevice. The method also includes generating an OFDMA data unit for theWLAN communication channel. The OFDMA unit includes a preamble portionand a data portion. The preamble portion includes a legacy portion thatspans the first OFDM frequency sub-band and the second OFDM frequencysub-band using a legacy tone spacing and a legacy tone plan, a firstnon-legacy portion that spans the first OFDM frequency sub-band and thesecond OFDM frequency sub-band using the legacy tone spacing and thelegacy tone plan, a second non-legacy portion that spans the first OFDMfrequency sub-band using a non-legacy tone spacing and a non-legacy toneplan, and a third non-legacy portion that spans the second OFDMfrequency sub-band using the non-legacy tone spacing and the non-legacytone plan.

In another embodiment, an apparatus includes a network interface devicehaving one or more integrated circuits. The one or more integratedcircuits are configured to assign a plurality of different OFDMfrequency sub-bands for a WLAN communication channel to a plurality ofdevices including a first device and second device. The plurality ofdifferent OFDM frequency sub-bands includes at least a first OFDMfrequency sub-band assigned to the first device and a second OFDMfrequency sub-band assigned to the second device. The one or moreintegrated circuits are also configured to generate an OFDMA data unitfor the WLAN communication channel. The OFDMA unit includes a preambleportion and a data portion. The preamble portion includes a legacyportion that spans the first OFDM frequency sub-band and the second OFDMfrequency sub-band using a legacy tone spacing and a legacy tone plan, afirst non-legacy portion that spans the first OFDM frequency sub-bandand the second OFDM frequency sub-band using the legacy tone spacing andthe legacy tone plan, a second non-legacy portion that spans the firstOFDM frequency sub-band using a non-legacy tone spacing and a non-legacytone plan, and a third non-legacy portion that spans the second OFDMfrequency sub-band using the non-legacy tone spacing and the non-legacytone plan.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram of an example wireless local area network(WLAN), according to an embodiment.

FIGS. 2A and 2B are diagrams of a prior art data unit format.

FIG. 3 is a diagram of another prior art data unit format.

FIG. 4 is a diagram of another prior art data unit format.

FIG. 5 is a diagram of another prior art data unit format.

FIG. 6A is a group of diagrams of modulations used to modulate symbolsin a prior art data unit.

FIG. 6B is a group of diagrams of modulations used to modulate symbolsin an example data unit, according to an embodiment.

FIGS. 7A, 7B, and 7C are diagrams illustrating example orthogonalfrequency division multiplexing (OFDM) sub-channel blocks of anorthogonal frequency division multiple access (OFDMA) data unit for an80 MHz communication channel, according to an embodiment.

FIG. 8 is a diagram of an example tone plan for a 32-FFT tone plan,according to an embodiment.

FIG. 9A is a diagram illustrating an example OFDMA data unit, accordingto an embodiment.

FIG. 9B is a diagram illustrating an example portion of an OFDMA dataunit, according to another embodiment.

FIG. 10 is a block diagram of an example PHY processing unit forgenerating OFDMA data units or portions thereof, according to anotherembodiment.

FIG. 11 is a block diagram of an example PHY processing unit forgenerating OFDMA data units or portions thereof using channel bonding,according to an embodiment.

FIG. 12 is a block diagram of an example PHY processing unit forgenerating OFDMA data units or portions thereof using channel bonding,according to another embodiment.

FIG. 13 is a block diagram of an example PHY processing unit forgenerating OFDMA data units or portions thereof using channel bonding,according to yet another embodiment.

FIG. 14A is a diagram illustrating an example OFDMA data unit for achannel bonding scenario, according to an embodiment.

FIG. 14B is a diagram illustrating an example portion of an OFDMA dataunit for a channel bonding scenario, according to another embodiment.

FIG. 15A is a block diagram of an example PHY processing unit forgenerating OFDMA data units or portions thereof using channel bonding,according to an embodiment.

FIG. 15B is a block diagram of an example PHY processing unit forgenerating OFDMA data units or portions thereof using channel bonding,according to another embodiment.

FIG. 16 is a block diagram of an example downlink OFDMA data unit,according to an embodiment.

FIG. 17A is a diagram illustrating a regular mode data unit, accordingto an embodiment.

FIG. 17B is a diagram illustrating a multiple access mode data unit,according to an embodiment.

FIGS. 18A-18B are diagrams respectively illustrating two possibleformats of a long training field, according to two example embodiments.

FIG. 19A is a diagram illustrating a non-legacy signal field of theregular mode data unit of FIG. 17A, according to an embodiment.

FIG. 19B is a diagram illustrating a non-legacy signal field of themultiple access mode data unit of FIG. 17B, according to an embodiment.

FIG. 20A is a block diagram illustrating a multiple access mode dataunit, according to an embodiment.

FIG. 20B is a diagram illustrating a legacy signal field of the multipleaccess mode data unit of FIG. 20A, according to one embodiment.

FIG. 20C is a diagram illustrating a Fast Fourier Transform (FFT) windowfor the legacy signal field of FIG. 14B at the legacy receiving device,according to an embodiment.

FIG. 21 is a block diagram illustrating format of a non-legacy signalfield, according to an embodiment.

FIG. 22 is a block diagram of an example downlink OFDMA data unit,according to another embodiment.

FIG. 23 is a block diagram of an example downlink OFDMA data unit usingreduced tone spacing, according to an embodiment.

FIG. 24 is a block diagram of an example uplink OFDMA data unit,according to an embodiment.

FIGS. 25A and 25B are block diagrams of example uplink OFDM signals fromdifferent client stations, according to an embodiment.

FIG. 26A is a block diagram of an example OFDMA data unit that includesa legacy OFDM signal, according to an embodiment.

FIG. 26B is a block diagram of an example OFDMA data unit that includesa legacy OFDM signal, according to another embodiment.

FIGS. 27A, 27B, 27C, and 27D are example diagrams of short trainingfields for OFDMA data units, according to various embodiments.

FIG. 28 is a flow diagram of an example method for generating an OFDMAdata unit, according to an embodiment.

FIG. 29 is a flow diagram of an example method for generating an OFDMAdata unit, according to another embodiment.

FIG. 30 is a flow diagram of an example method for generating an OFDMAdata unit, according to an embodiment.

FIG. 31 is a flow diagram of an example method for generating a portionof an OFDMA data unit, according to an embodiment.

FIG. 32 is a flow diagram of an example method for generating a portionof an OFDMA data unit, according to another embodiment.

DETAILED DESCRIPTION

In embodiments described below, a wireless network device such as anaccess point (AP) of a wireless local area network (WLAN) transmits datastreams to a plurality of client stations. The AP is configured tooperate with client stations according to at least a first communicationprotocol. The first communication protocol is sometimes referred toherein as “high efficiency Wi-Fi,” “HEW” communication protocol, or802.11ax communication protocol. In some embodiments described below,one or more client stations transmit respective data streams to an AP.In some embodiments, different client stations in the vicinity of the APare configured to operate according to one or more other communicationprotocols which define operation in the same frequency band as the HEWcommunication protocol but with generally lower data throughputs. Thelower data throughput communication protocols (e.g., IEEE 802.11a, IEEE802.11n, and/or IEEE 802.11ac) are collectively referred herein as“legacy” communication protocols. In at least some embodiments, thelegacy communication protocols are generally deployed in indoorcommunication channels, and the HEW communication protocol is at leastsometimes deployed for outdoor communications.

According to an embodiment, orthogonal frequency division multiplex(OFDM) symbols transmitted by the AP are generated according to amultiple access mode that partitions a WLAN communication channel intoOFDM tone blocks for simultaneous communication with multiple clientstations. Simultaneous transmission with the client stations provides areduction in overhead due to non-user data within a data unit, such astraining fields and signal fields, in some embodiments. In anembodiment, the HEW communication protocol defines a regular mode andmultiple access mode. The regular mode is generally used for a data unittransmitted to a single client station, while the multiple access modeis generally used for data units transmitted to multiple clientstations, in an embodiment.

In an embodiment, a plurality of OFDM tone blocks for a WLANcommunication channel are assigned to a plurality of devices. Anorthogonal frequency division multiple access (OFDMA) data unit isgenerated for the WLAN communication channel. In some embodiments, theOFDMA unit includes a preamble portion and a data portion, the preambleportion having i) at least a legacy portion that spans the entire WLANcommunication channel, ii) a first non-legacy portion that spans thefirst OFDM tone block, and iii) a second non-legacy portion that spansthe second OFDM tone block. In some embodiments, the preamble is used,at least in part, to signal, to a receiving device, various parametersused for transmission of the data portion. In various embodiments, thepreamble of a data unit is used to signal, to a receiving device, themode being utilized for the OFDMA data unit and/or which receivingdevice is intended to decode a particular portion of the OFDMA dataunit. In some embodiments, a same preamble format is used in the regularmode as in the multiple access mode. In one such embodiment, thepreamble includes an indication set to indicate whether the regular modeor the multiple access mode is used. In an embodiment, the receivingdevice determines the mode being utilized based on the indication in thepreamble of the data unit, and then decodes an indicated portion of thedata unit (e.g., the data portion, or a portion of the preamble and thedata portion). In another embodiment, a preamble used in the multipleaccess mode is formatted differently from a preamble used in the regularmode. For example, the preamble used in the multiple access mode isformatted such that the receiving device can automatically (e.g., priorto decoding) detect that the data unit corresponds to the multipleaccess mode.

Additionally, in at least some embodiments, a preamble of an OFDMA dataunit in the regular mode and/or in the multiple access mode is formattedsuch that a client station that operates according to a legacy protocol,and not the HEW communication protocol, is able to determine certaininformation regarding the OFDMA data unit, such as a duration of thedata unit, and/or that the data unit does not conform to the legacyprotocol. Additionally, a preamble of the data unit is formatted suchthat a client station that operates according to the HEW protocol isable to determine the data unit conforms to the HEW communicationprotocol and whether the data unit is formatted according to the regularmode or the multiple access mode, in an embodiment. Similarly, a clientstation configured to operate according to the HEW communicationprotocol also transmits data units such as described above, in anembodiment.

In at least some embodiments, data units formatted such as describedabove are useful, for example, with an AP that is configured to operatewith client stations according to a plurality of different communicationprotocols and/or with WLANs in which a plurality of client stationsoperate according to a plurality of different communication protocols.Continuing with the example above, a communication device configured tooperate according to both the HEW communication protocol (including theregular mode and the multiple access mode) and a legacy communicationprotocol is able to determine that a given data unit is formattedaccording to the HEW communication protocol and not the legacycommunication protocol, and further, to determine that the data unit isformatted according to the multiple access mode and not the regularmode. Similarly, a communication device configured to operate accordingto a legacy communication protocol but not the HEW communicationprotocol is able to determine that the data unit is not formattedaccording to the legacy communication protocol and/or determine aduration of the data unit.

FIG. 1 is a block diagram of an example wireless local area network(WLAN) 10, according to an embodiment. An AP 14 includes a hostprocessor 15 coupled to a network interface 16. The network interface 16includes a medium access control (MAC) processing unit 18 and a physicallayer (PHY) processing unit 20. The PHY processing unit 20 includes aplurality of transceivers 21, and the transceivers 21 are coupled to aplurality of antennas 24. Although three transceivers 21 and threeantennas 24 are illustrated in FIG. 1, the AP 14 includes other suitablenumbers (e.g., 1, 2, 4, 5, etc.) of transceivers 21 and antennas 24 inother embodiments. In one embodiment, the MAC processing unit 18 and thePHY processing unit 20 are configured to operate according to a firstcommunication protocol (e.g., HEW communication protocol), including atleast a first mode and a second mode of the first communicationprotocol. In some embodiments, the first mode corresponds to a multipleaccess mode that partitions a wider communication channel into narrowersub-bands or OFDM sub-channel blocks, and different data streams aretransmitted in respective OFDM sub-channel blocks to respective clientstations. OFDM sub-channel blocks are sometimes referred to herein as“OFDM tone blocks” (e.g., a block of adjacent tones or sub-carriers).The multiple access mode is configured to provide an orthogonalfrequency division multiple access (OFDMA) data unit that includes atleast a portion of separate data streams to respective client stations.In another embodiment, the MAC processing unit 18 and the PHY processingunit 20 are also configured to operate according to a secondcommunication protocol (e.g., IEEE 802.11ac Standard). In yet anotherembodiment, the MAC processing unit 18 and the PHY processing unit 20are additionally configured to operate according to the secondcommunication protocol, a third communication protocol, and/or a fourthcommunication protocol (e.g., the IEEE 802.11a Standard and/or the IEEE802.11n Standard).

The WLAN 10 includes a plurality of client stations 25. Although fourclient stations 25 are illustrated in FIG. 1, the WLAN 10 includes othersuitable numbers (e.g., 1, 2, 3, 5, 6, etc.) of client stations 25 invarious scenarios and embodiments. At least one of the client stations25 (e.g., client station 25-1) is configured to operate at leastaccording to the first communication protocol. In some embodiments, atleast one of the client stations 25 is not configured to operateaccording to the first communication protocol but is configured tooperate according to at least one of the second communication protocol,the third communication protocol, and/or the fourth communicationprotocol (referred to herein as a “legacy client station”).

The client station 25-1 includes a host processor 26 coupled to anetwork interface 27. The network interface 27 includes a MAC processingunit 28 and a PHY processing unit 29. The PHY processing unit 29includes a plurality of transceivers 30, and the transceivers 30 arecoupled to a plurality of antennas 34. Although three transceivers 30and three antennas 34 are illustrated in FIG. 1, the client station 25-1includes other suitable numbers (e.g., 1, 2, 4, 5, etc.) of transceivers30 and antennas 34 in other embodiments.

According to an embodiment, the client station 25-4 is a legacy clientstation, i.e., the client station 25-4 is not enabled to receive andfully decode a data unit that is transmitted by the AP 14 or anotherclient station 25 according to the first communication protocol.Similarly, according to an embodiment, the legacy client station 25-4 isnot enabled to transmit data units according to the first communicationprotocol. On the other hand, the legacy client station 25-4 is enabledto receive and fully decode and transmit data units according to thesecond communication protocol, the third communication protocol, and/orthe fourth communication protocol.

In an embodiment, one or both of the client stations 25-2 and 25-3, hasa structure the same as or similar to the client station 25-1. In anembodiment, the client station 25-4 has a structure similar to theclient station 25-1. In these embodiments, the client stations 25structured the same as or similar to the client station 25-1 have thesame or a different number of transceivers and antennas. For example,the client station 25-2 has only two transceivers and two antennas (notshown), according to an embodiment.

In various embodiments, the PHY processing unit 20 of the AP 14 isconfigured to generate data units conforming to the first communicationprotocol and having formats described herein. The transceiver(s) 21is/are configured to transmit the generated data units via theantenna(s) 24. Similarly, the transceiver(s) 21 is/are configured toreceive data units via the antenna(s) 24. The PHY processing unit 20 ofthe AP 14 is configured to process received data units conforming to thefirst communication protocol and having formats described hereinafterand to determine that such data units conform to the first communicationprotocol, according to various embodiments.

In various embodiments, the PHY processing unit 29 of the client device25-1 is configured to generate data units conforming to the firstcommunication protocol and having formats described herein. Thetransceiver(s) 30 is/are configured to transmit the generated data unitsvia the antenna(s) 34. Similarly, the transceiver(s) 30 is/areconfigured to receive data units via the antenna(s) 34. The PHYprocessing unit 29 of the client device 25-1 is configured to processreceived data units conforming to the first communication protocol andhaving formats described hereinafter and to determine that such dataunits conform to the first communication protocol, according to variousembodiments.

FIG. 2A is a diagram of a prior art OFDM data unit 200 that the AP 14 isconfigured to transmit to the legacy client station 25-4 via orthogonalfrequency division multiplexing (OFDM) modulation, according to anembodiment. In an embodiment, the legacy client station 25-4 is alsoconfigured to transmit the data unit 200 to the AP 14. The data unit 200conforms to the IEEE 802.11a Standard and occupies a 20 Megahertz (MHz)band. The data unit 200 includes a preamble having a legacy shorttraining field (L-STF) 202, generally used for packet detection, initialsynchronization, and automatic gain control, etc., and a legacy longtraining field (L-LTF) 204, generally used for channel estimation andfine synchronization. The data unit 200 also includes a legacy signalfield (L-SIG) 206, used to carry certain physical layer (PHY) parameterswith the data unit 200, such as modulation type and coding rate used totransmit the data unit, for example. The data unit 200 also includes adata portion 208. FIG. 2B is a diagram of example data portion 208 (notlow density parity check encoded), which includes a service field, ascrambled physical layer service data unit (PSDU), tail bits, andpadding bits, if needed. The data unit 200 is designed for transmissionover one spatial or space-time stream in a single input single output(SISO) channel configuration.

FIG. 3 is a diagram of a prior art OFDM data unit 300 that the AP 14 isconfigured to transmit to the legacy client station 25-4 via orthogonalfrequency domain multiplexing (OFDM) modulation, according to anembodiment. In an embodiment, the legacy client station 25-4 is alsoconfigured to transmit the data unit 300 to the AP 14. The data unit 300conforms to the IEEE 802.11n Standard, occupies a 20 MHz band, and isdesigned for mixed mode situations, i.e., when the WLAN includes one ormore client stations that conform to the IEEE 802.11a Standard but notthe IEEE 802.11n Standard. The data unit 300 includes a preamble havingan L-STF 302, an L-LTF 304, an L-SIG 306, a high throughput signal field(HT-SIG) 308, a high throughput short training field (HT-STF) 310, and Mdata high throughput long training fields (HT-LTFs) 312, where M is aninteger generally determined by the number of spatial streams (N_(sts))used to transmit the data unit 300 in a multiple input multiple output(MIMO) channel configuration. In particular, according to the IEEE802.11n Standard, the data unit 300 includes two HT-LTFs 312 if the dataunit 300 is transmitted using two spatial streams, and four HT-LTFs 312is the data unit 300 is transmitted using three or four spatial streams.An indication of the particular number of spatial streams being utilizedis included in the HT-SIG field 308. The data unit 300 also includes adata portion 314.

FIG. 4 is a diagram of a prior art OFDM data unit 400 that the AP 14 isconfigured to transmit to the legacy client station 25-4 via orthogonalfrequency domain multiplexing (OFDM) modulation, according to anembodiment. In an embodiment, the legacy client station 25-4 is alsoconfigured to transmit the data unit 400 to the AP 14. The data unit 400conforms to the IEEE 802.11n Standard, occupies a 20 MHz band, and isdesigned for “Greenfield” situations, i.e., when the WLAN does notinclude any client stations that conform to the IEEE 802.11a Standard,and only includes client stations that conform to the IEEE 802.11nStandard. The data unit 400 includes a preamble having a high throughputGreenfield short training field (HT-GF-STF) 402, a first high throughputlong training field (HT-LTF1) 404, a HT-SIG 406, and M data HT-LTFs 408,where M is an integer which generally corresponds to a number of spatialstreams used to transmit the data unit 400 in a multiple input multipleoutput (MIMO) channel configuration. The data unit 400 also includes adata portion 410.

FIG. 5 is a diagram of a prior art OFDM data unit 500 that the AP 14 isconfigured to transmit to the legacy client station 25-4 via orthogonalfrequency domain multiplexing (OFDM) modulation, according to anembodiment. In an embodiment, the legacy client station 25-4 is alsoconfigured to transmit the data unit 500 to the AP 14. The data unit 500conforms to the IEEE 802.11ac Standard and is designed for “Mixed field”situations. The data unit 500 occupies a 20 MHz bandwidth. In otherembodiments or scenarios, a data unit similar to the data unit 500occupies a different bandwidth, such as a 40 MHz, an 80 MHz, or a 160MHz bandwidth. The data unit 500 includes a preamble having an L-STF502, an L-LTF 504, an L-SIG 506, two first very high throughput signalfields (VHT-SIGAs) 508 including a first very high throughput signalfield (VHT-SIGA1) 508-1 and a second very high throughput signal field(VHT-SIGA2) 508-2, a very high throughput short training field (VHT-STF)510, M very high throughput long training fields (VHT-LTFs) 512, where Mis an integer, and a second very high throughput signal field(VHT-SIG-B) 514. The data unit 500 also includes a data portion 516.

FIG. 6A is a set of diagrams illustrating modulation of the L-SIG,HT-SIG1, and HT-SIG2 fields of the data unit 300 of FIG. 3, as definedby the IEEE 802.11n Standard. The L-SIG field is modulated according tobinary phase shift keying (BPSK), whereas the HT-SIG1 and HT-SIG2 fieldsare modulated according to BPSK, but on the quadrature axis (Q-BPSK). Inother words, the modulation of the HT-SIG1 and HT-SIG2 fields is rotatedby 90 degrees as compared to the modulation of the L-SIG field.

FIG. 6B is a set of diagrams illustrating modulation of the L-SIG,VHT-SIGA1, and VHT-SIGA2 fields of the data unit 500 of FIG. 5, asdefined by the IEEE 802.11ac Standard. Unlike the HT-SIG1 field in FIG.6A, the VHT-SIGA1 field is modulated according to BPSK, same as themodulation of the L-SIG field. On the other hand, the VHT-SIGA2 field isrotated by 90 degrees as compared to the modulation of the L-SIG field.

FIGS. 7A, 7B, and 7C are diagrams illustrating example OFDM sub-channelblocks (or OFDM tone blocks) for an 80 MHz communication channel,according to an embodiment. In various embodiments, the communicationchannel is partitioned by an AP, such as the AP 14, into a plurality ofOFDM tone blocks. In an embodiment, the AP assigns the plurality of OFDMtone blocks to one or more client stations, such as the client stations25-1, 25-2, 25-3, or 25-4. In a downlink direction, the AP generates andtransmits an OFDMA data unit that spans the communication channel andincludes an OFDM data unit for one or more client stations, in anembodiment. In this embodiment, the OFDMA data unit includes an OFDMdata unit for each client station which has been assigned an OFDM toneblock via the corresponding tone block. In an embodiment, the OFDMA dataunit omits an OFDM data unit for a client station, for example, if nodata is to be transmitted to an idle client station. In this embodiment,the corresponding OFDM tone block for the idle client station is set tozero or the OFDMA data unit omits the corresponding OFDM tone block.

In FIG. 7A, a communication channel 700 is partitioned into fourcontiguous OFDM tone blocks 701, 702, 703, and 704, each having abandwidth of 20 MHz, according to an embodiment. The OFDM tone blocks701, 702, 703, and 704 are assigned to one or more client stations,according to various embodiments. In the embodiment shown in FIG. 7A,the OFDM tone blocks 701, 702, 703, and 704 include independent datastreams for four client stations STA 1, STA 2, STA 3, and STA 4,respectively. In FIG. 7B, a communication channel 710 is partitionedinto three contiguous OFDM tone blocks 711, 712, and 713, according toan embodiment. Two OFDM tone blocks 711 and 712 each have a bandwidth of20 MHz. The remaining OFDM tone block 713 has a bandwidth of 40 MHz. TheOFDM tone blocks 711, 712, and 713 are assigned to, and includeindependent data streams for, three client stations STA 1, STA 2, andSTA 3, respectively. In FIG. 7C, a communication channel 720 ispartitioned into four contiguous OFDM tone blocks 721, 722, 723, and724, according to an embodiment. The OFDM tone blocks 721 and 722 eachhave a bandwidth of 10 MHz and thus together span a bandwidth equal to asmallest channel bandwidth of a legacy WLAN communication protocol(i.e., 20 MHz). The OFDM tone block 723 has a bandwidth of 20 MHz. TheOFDM tone block 724 has a bandwidth of 40 MHz. The OFDM tone blocks 722and 724 are assigned to, and include independent data streams for, twoclient stations STA 2 and STA 3, respectively. The OFDM tone blocks 721and 723, which are separated in frequency by the OFDM tone block 722,are assigned to and include portions of a data stream for client stationSTA 1 and use a channel bonding technique, as described herein.

Although in FIGS. 7A, 7B, and 7C, the OFDM tone blocks are contiguousacross the corresponding communication channel, in other embodiments theOFDM tone blocks are not contiguous across the communication channel(i.e., there are one or more gaps between the OFDM tone blocks). In anembodiment, each gap is at least as wide as one of the OFDM tone blocks.In another embodiment, at least one gap is less than the bandwidth of anOFDM tone block. In another embodiment, at least one gap is at least aswide as 1 MHz. In an embodiment, different OFDM tone blocks aretransmitted in different channels defined by the IEEE 802.11a and/or802.11n Standards. In one embodiment, the AP includes a plurality ofradios and different OFDM tone blocks are transmitted using differentradios.

In an embodiment, for a plurality of data streams transmitted by an APin different OFDM tone blocks, different data streams are transmitted atdifferent data rates when, for example, signal strength, SNR,interference power, etc., varies between client devices. Additionally,for a plurality of data streams transmitted by an AP in different OFDMtone blocks, the amount of data in different data streams is oftendifferent. Thus, one transmitted data stream can end before another. Insuch situations, the data in an OFDM tone block corresponding to thedata stream that is ended is set to zero or some other suitablepredetermined value, according to an embodiment.

An OFDM signal comprising a plurality of OFDM tone blocks to transmitindependent data streams as described above is also referred to hereinas an orthogonal frequency division multiple access (OFDMA) signals.According to an embodiment, a WLAN utilizes downlink OFDMA data unitsand uplink OFDMA data units. Downlink OFDMA data units are transmittedsynchronously from a single AP to multiple client stations (i.e.,point-to-multipoint). An uplink OFDMA data unit is transmitted bymultiple clients stations jointly to a single AP (i.e.,multipoint-to-point). Frame formats, modulation and coding schemes(MCS), a number of space time streams, tone spacing, and/or signalingschemes for downlink OFDMA and uplink OFDMA are different, according tosome embodiments. In some embodiments, OFDM data units within an OFDMAdata unit have different MCSs, numbers of space time streams, tonespacing, and/or signaling schemes.

Various embodiments of a PHY frame format for downlink and/or uplinkOFDMA data units are described with respect to FIGS. 16, 22, 23, 24,25A, 25B, 26A, and 26B. In the following embodiments, OFDM tone blockshave a format substantially similar to the PHY format specified in theIEEE 802.11ac Standard. In other embodiments, OFDM tone blocks have aformat substantially similar to another communication protocol such asthe PHY format specified in the IEEE 802.11a Standard, the IEEE 802.11nStandard, or a communication protocol not yet standardized.

In an embodiment, OFDM data units for OFDM tone blocks that span abandwidth greater than or equal to 20 MHz are generated using a same MCSand “legacy” tone plan as defined in IEEE 802.11n and/or IEEE 802.11ac.As referred to herein, a tone plan is a predetermined sequence ofindices that indicate which OFDM tones, corresponding to a fast Fouriertransform (FFT) of suitable size, are designated for data tones, pilottones, and/or guard tones. For example, in an embodiment, an OFDM toneblock that spans 20 MHz uses an FFT of size 64 with a legacy tone planfor IEEE 802.11ac having four pilot tones (at indices −21, −7, +7, and+21), a direct current tone (at index 0), guard tones (at indices −32 to−29 and 29 to 31), and 52 data tones (at the remaining indices). In someembodiments, OFDM tone blocks that span 40 MHz, 80 MHz, or 160 MHz useFFT sizes of 128, 256, and 512, respectively, with corresponding legacytone plans as defined in IEEE 802.11ac.

In some embodiments, a communication channel is partitioned to includeOFDM tone blocks that span a bandwidth smaller than 20 MHz, such as 10MHz, 5 MHz, or 2.5 MHz. In an embodiment, an OFDM tone block that spansa bandwidth smaller than 20 MHz uses a tone plan different from a legacytone plan. FIG. 8 is a diagram of an example tone plan 800 for an OFDMtone block that spans a 10 MHz bandwidth and uses an FFT size of 32,according to an embodiment. The tone plan 800 has two pilot tones (atindices −7 and +7), a direct current tone (at index 0), guard tones802-1 and 802-2 (at indices −16 to −14 and 14 to 15), and 24 data tones804-1, 804-2, 804-3, and 804-4 (at the remaining indices).

FIG. 9A is a diagram illustrating an example OFDMA data unit for an 80MHz communication channel, according to an embodiment. In an uplinkdirection, a client station, such as the client station 25-1, generatesand transmits a portion of an OFDMA data unit 900 that spans thecommunication channel using an FFT size of 256 (e.g., a “full-size”FFT), in an embodiment. In this embodiment, the OFDMA data unit 900includes an OFDMA data unit portion 902 that spans the correspondingassigned OFDM tone block and zero tones 904-1, 904-2, and 904-3 insertedinto unassigned OFDM tone blocks for the FFT. FIG. 9B is a diagramillustrating an example portion of an OFDMA data unit for an 80 MHzcommunication channel, according to another embodiment. In thisembodiment, the client station generates and transmits an OFDMA dataunit portion 910 that spans only the OFDM tone block assigned to theclient station using a suitable FFT size (i.e., 64 FFT size for 20 MHz,128 FFT size for 40 MHz, etc.).

FIG. 10 is a block diagram of an example PHY processing unit 1000 forgenerating an OFDMA data unit or an OFDMA data unit portion, accordingto various embodiments. Referring to FIG. 1, the AP 14 and the clientstation 25-1, in an embodiment, each include a PHY processing unit suchas the PHY processing unit 1000. In various embodiments and/orscenarios, the PHY processing unit 1000 generates OFDM data units suchas one of the data units of FIG. 7A, 7B, 7C, 9A, or 9B, for example. ThePHY processing unit 1000 includes a scrambler 1002 that generallyscrambles an information bit stream to be transmitted in order to reducethe occurrence of long sequences of ones or zeros. An FEC encoder 1004encodes scrambled information bits to generate encoded data bits. In oneembodiment, the FEC encoder 1004 includes a binary convolutional code(BCC) encoder. In another embodiment, the FEC encoder 1004 includes abinary convolutional encoder followed by a puncturing block. In yetanother embodiment, the FEC encoder 1004 includes a low density paritycheck (LDPC) encoder.

A stream parser 1006 receives and parses the encoded data bits into oneor more spatial streams, in an embodiment. For each spatial stream (twospatial streams in the embodiment shown in FIG. 10), a constellationmapper 1010 maps the encoded data bits to constellation pointscorresponding to different subcarriers of an OFDM symbol. Morespecifically, for each spatial stream, the constellation mapper 1010translates every bit sequence of length log₂(M) into one of Mconstellation points. In some embodiments, the PHY processing unit 1000includes a plurality of parallel processing paths, for example, one pathfor each spatial stream. In other embodiments, a single processing pathis used for the spatial streams.

In an embodiment where the FEC encoder 1004 is a BCC encoder,interleavers 1008 receive the encoded data bits and interleave the bits(i.e., changes the order of the bits), prior to the constellationmappers 1010, to prevent long sequences of adjacent noisy bits fromentering a decoder at the receiver. In another embodiment, theinterleavers 1008 are omitted. In an embodiment where the FEC encoder1004 is an LDPC encoder, LDPC tone mappers 1012 reorder constellationpoints according to a tone remapping function. The tone remappingfunction is generally defined such that consecutive coded informationbits or blocks of information bits are mapped onto nonconsecutive tonesin the OFDM symbol to facilitate data recovery at the receiver in casesin which consecutive OFDM tones are adversely affected duringtransmission. In some embodiments, the LDPC tone mappers 1012 areomitted.

The outputs of the constellation mappers 1010 for each stream (or LDPCtone mappers 1012, where included) are operated on by a space time blockcoder (STBC) 1014, in an embodiment. The space-time block coder 1014takes a single constellation symbol output and maps it onto multipletransmission chains for transmission by separate radio transmitters,transforming the spatial streams into space-time streams, in anembodiment. In embodiments or situations in which the PHY processingunit 1000 operates to generate data units for transmission via multiplespatial streams, one or more cyclic shift diversity (CSD) units 1016inserts a cyclic shift into all but one of the spatial streams toprevent unintentional beamforming. A spatial mapper 1018 maps thespace-time streams onto a transmission chain, in an embodiment. The PHYprocessing unit 1000 includes an inverse discrete Fourier transform(IDFT) processor 1020 for each transmission chain, in an embodiment. Inan embodiment, the FEC encoder 1004, stream parser 1006, interleavers1008, constellation mappers 1010, LDPC tone mappers 1012, STBC 1014, CSDunits 1016, and spatial mapper 1018 operate according to the IEEE802.11ac protocol.

The IDFT processor 1020 receives pilot tones from a pilot generator 1022and spatially mapped constellation points from the spatial mapper 1018,in an embodiment. The IDFT processor 1020 converts a block of thespatially mapped constellation points corresponding to data tones withinan OFDM tone block and pilot tones to a time-domain signal, in anembodiment. In some embodiments, the IDFT processor 1020 processes oneor more tones from a tone input 1024 to be included in the time-domainsignal. For example, in an embodiment, the PHY processing unit 1000generates an OFDMA data unit having OFDM data units for multiple usersto be transmitted from an AP (i.e., a downstream OFDMA data unit). Inthis embodiment, the tone input 1024 provides data tones and/or pilottones corresponding to another user which are generated separately. TheIDFT processor 1020 thus performs the IDFT jointly for all tones for allusers simultaneously.

In another embodiment, the PHY processing unit 1000 generates a portionof an OFDMA data unit to be transmitted from a client station to an AP(i.e., a portion of an uplink OFDMA data unit). In an embodiment, thetone input 1024 provides zero tones for unassigned OFDM tone blocks forgeneration of the OFDMA data unit using a full-size FFT, as describedabove with respect to FIG. 9A. In another embodiment, the client stationgenerates and transmits an OFDMA data unit portion that spans only theOFDM tone block assigned to the client station using a suitable FFTsize, as described above with respect to FIG. 9B.

FIG. 11 is a block diagram of an example PHY processing unit 1100 forgenerating an OFDMA data unit or an OFDMA data unit portion usingchannel bonding, according to an embodiment. The PHY processing unit1100 is configured to provide an OFDMA data unit, or portion thereof,where a client station has been assigned two or more non-contiguous OFDMtone blocks (“bonded channels”). As described above with respect toFIGS. 7A, 7B, 7C, a communication channel is partitioned into aplurality of OFDM tone blocks. As shown in FIG. 7C, the OFDM tone blocks721 and 723, which are separated in frequency by the OFDM tone block722, are assigned to and include portions of a data stream for clientstation STA 1 and use a channel bonding technique. In some embodiments,the PHY processing unit 1100 provides a separate encoder and modulatorto allow for different MCS values for different OFDM tone blocks. In anembodiment, the PHY processing unit 1100 includes the scrambler 1002,pilot generator 1022, tone inputs 1024, and IDFT processors 1020, asdescribed above with respect to FIG. 10. The PHY processing unit 1100further includes a plurality of processing paths 1150 that operatesubstantially in parallel and correspond to the assigned OFDM toneblocks, in an embodiment. In another embodiment, the processing path1150 is a single processing path. The processing paths 1150 each includethe FEC encoder 1004, stream parser 1006, interleavers 1008,constellation mappers 1010, LDPC tone mappers 1012, STBC 1014, CSD units1016, and spatial mapper 1018, as described above with respect to FIG.10.

In an embodiment, the scrambler 1002 provides scrambled information bitsto a segment parser 1140. The segment parser 1140 separates thescrambled information bits into a plurality of segments and passes eachsegment to an assigned OFDM tone block, in an embodiment. In anembodiment, the AP assigns same size OFDM tone blocks to a clientstation, such as 10 MHz+10 MHz, 20 MHz+20 MHz, or other suitablecombinations. In another embodiment, the AP assigns different size OFDMtone blocks to a client station, such as 10 MHz+20 MHz+20 MHz, 10 MHz+40MHz, or other suitable combinations. In other embodiments, additionalOFDM tone blocks are bonded together, for example, three or four OFDMtone blocks are bonded together.

In an embodiment, each OFDM tone block that is a bonded channel uses asame tone plan as in a non-bonded channel scenario. For example, in anembodiment, a 10 MHz OFDM tone block corresponds to the tone plan shownin FIG. 8 when bonded with a 20 MHz OFDM tone block that uses an FFT ofsize 64 with a legacy tone plan for IEEE 802.11ac. In an embodiment,each OFDM tone block assigned to a same client station uses a same MCSvalue. In some embodiments, each OFDM tone block assigned to a sameclient station has a different MCS value. In an embodiment, each OFDMtone block assigned to a client station has a same number of space-timestreams.

FIG. 12 is a block diagram of an example PHY processing unit 1200 forgenerating an OFDMA data unit or an OFDMA data unit portion usingchannel bonding, according to another embodiment. The PHY processingunit 1200 is configured to provide an OFDMA data unit, or portionthereof, where a client station has been assigned two or morenon-contiguous OFDM tone blocks. In an embodiment, the PHY processingunit 1200 includes the scrambler 1002, FEC encoder 1004, stream parser1006, pilot generator 1022, tone inputs 1024, and IDFT processors 1020as described above with respect to FIG. 10. In the embodiment shown inFIG. 12, the PHY processing unit 1200 provides a joint encoder for eachuser, for example, the FEC encoder 1004 performs joint encoding acrossthe OFDM tone blocks assigned to a single user. A segment parser 1240separates the spatial streams from the stream parser 1006 into aplurality of stream segments. The PHY processing unit 1200 includes aplurality of processing paths 1250 that operate substantially inparallel and correspond to the assigned OFDM tone blocks, in anembodiment. In another embodiment, the processing path 1250 is a singleprocessing path. The processing paths 1250 each include the interleavers1008, constellation mappers 1010, LDPC tone mappers 1012, STBC 1014, CSDunits 1016, and spatial mapper 1018, as described above with respect toFIG. 10. The segment parser 1240 passes a spatial stream for an OFDMtone block from the stream parser 1006 to a corresponding processingpath 1250, in an embodiment.

FIG. 13 is a block diagram of an example PHY processing unit 1300 forgenerating an OFDMA data unit or an OFDMA data unit portion usingchannel bonding, according to yet another embodiment. The PHY processingunit 1300 is configured to provide an OFDMA data unit, or portionthereof, where a client station has been assigned two or morenon-contiguous OFDM tone blocks using a same MCS value for each OFDMtone block. In an embodiment, the PHY processing unit 1300 includes thescrambler 1002, FEC encoder 1004, stream parser 1006, interleavers 1008,constellation mappers 1010, LDPC tone mappers 1012, STBC 1014, CSD units1016, spatial mapper 1018, pilot generator 1022, tone inputs 1024, andIDFT processors 1020, as described above with respect to FIG. 10, andtone allocators 1340 configured to split spatial streams from thespatial mapper 1018 into the assigned OFDM tone blocks and provide thesplit spatial streams to the IDFT processors 1020.

FIG. 14A is a diagram illustrating an example OFDMA data unit for achannel bonding scenario of an 80 MHz communication channel, accordingto an embodiment. In an uplink direction, a PHY processing unit, such asthe PHY processing units 1100, 1200, or 1300, generates and transmits aportion of an OFDMA data unit 1400 that spans the communication channelusing an FFT size of 256 (e.g., a “full-size” FFT), in an embodiment. Inthis embodiment, the OFDMA data unit 1400 includes a first OFDMA dataunit portion 1402 that spans a first assigned OFDM tone block, a secondOFDMA data unit portion 1404 that spans a second assigned OFDM toneblock, and zero tones 1406-1 and 1406-2 inserted into unassigned OFDMtone blocks for the FFT.

FIG. 14B is a diagram illustrating an example portion of an OFDMA dataunit for a channel bonding scenario, according to another embodiment. Inthis embodiment, in an uplink direction, a PHY processing unit generatesand transmits an OFDMA data unit portion 1450 that spans only assignedOFDM tone blocks 1452 and 1454. In an embodiment, the PHY processingunit generates and transmits data over the OFDM tone blocks 1452 and1454 using separate transmission chains using suitable FFT sizes (i.e.,64 FFT size for 20 MHz, 128 FFT size for 40 MHz, etc.).

FIG. 15A is a block diagram of an example PHY processing unit 1500 forgenerating an OFDMA data unit or an OFDMA data unit portion usingchannel bonding, according to an embodiment. The PHY processing unit1500 is configured to generate and transmit an OFDMA data unit portion,such as the OFDMA data unit portion 1450, that spans only OFDM toneblocks assigned to a client station for an uplink transmission, in anembodiment. In some embodiments, the PHY processing unit 1500 includesseparate transmission chains 1502 for filtering and transmitting aportion of the OFDMA data unit portion via each assigned OFDM tone blockfor a client station. In an embodiment, the transmission chain 1502-1corresponds to the OFDM data unit 1452 and the transmission chain 1502-2corresponds to the OFDM data unit 1454. Each transmission chain 1502includes an IDFT processor 1520, such as the IDFT processor 1020 shownin FIG. 10, 11, 12, or 13, in various embodiments. The IDFT processor1520 performs an IDFT using only those tones within the correspondingassigned OFDM tone block, in an embodiment. A guard interval (GI)insertion and windowing unit 1542 prepends, to an OFDM symbol receivedfrom the IDFT processor 1520, a circular extension of the OFDM symboland smooths the edges of each symbol to increase spectral decay. Theoutput of the GI insertion and windowing unit 1542 is provided to ananalog and radio frequency (RF) unit 1544 that converts the signal toanalog signal and upconverts the signal to RF frequency fortransmission.

FIG. 15B is a block diagram of an example PHY processing unit 1550 forgenerating an OFDMA data unit or an OFDMA data unit portion usingchannel bonding, according to another embodiment. The PHY processingunit 1550 is configured to generate and transmit an OFDMA data unitportion, such as the OFDMA data unit portion 1450, that spans only OFDMtone blocks assigned to a client station for an uplink transmission, inan embodiment. In some embodiments, the PHY processing unit 1550includes separate transmission chains 1552 that correspond to eachassigned OFDM tone block for a client station. In an embodiment, thetransmission chain 1552-1 corresponds to the OFDM data unit 1452 and thetransmission chain 1552-2 corresponds to the OFDM data unit 1454. Eachtransmission chain 1552 includes an IDFT processor 1520 and GI insertionand windowing unit 1542 as described above with respect to FIG. 15A, invarious embodiments.

In an embodiment, the PHY processing unit 1550 is configured to filterand combine outputs from each GI insertion and windowing unit 1542 fortransmission by a single radio transmitter (i.e., a wideband radiotransmitter). For example, in an embodiment, each transmission chain1552 includes a low pass filter 1556, such as a digital filter, thatfilters an output from each GI insertion and windowing unit 1542. Asignal multiplier 1558 combines a phasor 1560 to provide a frequencyshift to all but one of the filtered outputs, in an embodiment. Thephasor 1560 is configured to provide a frequency shift that correspondsto the frequency separation between the assigned OFDM tone blocks, in anembodiment. Each filtered and shifted output is combined by a signalcombiner 1562 and provided as a single time-domain signal to an analogand RF unit 1554 that converts the signal to an analog signal andupconverts the analog signal to RF frequency for transmission.

FIG. 16 is a block diagram of an example OFDMA data unit 1600 that theAP 14 is configured to transmit over a communication channel to aplurality of client stations via OFDM modulation, according to anembodiment. The AP 14 partitions the communication channel into aplurality of OFDM tone blocks and assigns the OFDM tone blocks to aplurality of client stations as described above with respect to FIGS.7A, 7B, and 7C, in an embodiment. The OFDMA data unit 1600 conforms tothe first communication protocol. OFDMA data units that conform to thefirst communication protocol similar to the OFDMA data unit 1600 mayoccupy bandwidths such as 20 MHz, 40 MHz, 80 MHz, 160 MHz, 320 MHz, 640MHz, for example, or other suitable bandwidths, in other embodiments. Inthe embodiment of FIG. 16, the communication channel spans a bandwidthof 80 MHz and is partitioned into four equal-width OFDM tone blocks of20 MHz, which are assigned by the AP 14 to four client stations (e.g.,STA 1, STA 2, STA 3, and STA 4). In other embodiments, two or more OFDMtone blocks are assigned to a same client device using a channel bondingtechnique, as described above with respect to FIGS. 11, 12, 13, 14A,14B, 15A, and 15B. In some embodiments, the OFDM tone blocks spandifferent sub-bands within a communication channel, such as 2.5 MHz, 5MHz, 10 MHz, 20 MHz, 40 MHz, 80 MHz, 160 MHz sub-bands, or othersuitable sub-bands.

The OFDMA data unit 1600 includes OFDM data units 1640 corresponding toeach assigned OFDM tone block, in an embodiment. The OFDMA data unit1600 is suitable for “mixed mode” situations, i.e., when the WLAN 10includes a client station (e.g., the legacy client station 25-4) thatconforms to a legacy communication protocol, but not the firstcommunication protocol. The OFDMA data unit 1600 is utilized in othersituations as well, in some embodiments. In some embodiments, the OFDMdata units 1640 have PHY formats substantially similar to an IEEE 802.11standard, such as IEEE 802.11a, IEEE 802.11g, and/or IEEE 802.11n. In anembodiment, each OFDM data unit 1640 has a same PHY format. In anotherembodiment, the OFDMA data unit 1600 includes OFDM data units havingdifferent PHY formats.

The OFDMA data unit 1600, and thus each OFDM data unit 1640, includes apreamble portion 1601 and a data portion 1616 (e.g., a data field forthe corresponding client station), in an embodiment. In otherembodiments, the OFDM data unit 1640 omits the data portion 1616. Thepreamble portion 1601 of each OFDM data unit 1640 includes at least alegacy portion 1602 and a non-legacy portion 1603, in an embodiment. Thelegacy portion 1602 includes a legacy short training field (L-STF) 1604,a legacy long training field (L-LTF) 1605, and a legacy signal (L-SIG)field 1606, in an embodiment. Accordingly, each of the L-STF 1604, theL-LTF 1605, and the L-SIG 1606 are repeated over a corresponding numberof 20 MHz sub-bands of the whole bandwidth of the OFDMA data unit 1600,in an embodiment. In one embodiment, each OFDM tone block 1640 in FIG.16 has a width of 20 MHz. In another embodiment, each OFDM tone block1640 in FIG. 16 has a width of 40 MHz. According to an embodiment, if anOFDM tone block has a width of 40 MHz, the legacy portion 1602 (i.e.,L-STF, L-LTF, and L-SIG) is duplicated at upper and lower 20 MHz halves,with the sub-channels in the upper 20 MHz phase shifted by 90 degreeswith respect to the sub-channels in the lower 20 MHz.

The non-legacy portion 1603 includes an HEW signal (HEW-SIGA) field1608, an HEW short training field (HEW-STF) 1610, M HEW long trainingfields (HEW-LTFs) 1612, where M is an integer, and a third HEW signalfield (HEW-SIGB) 1614. Each of the L-STF 1604, the L-LTF 1605, the L-SIG1606, the HEW-SIGA 1608, the HEW-STF 1610, the M HEW-LTFs 1612, and theHEW-SIGB 1614 comprises an integer number of one or more OFDM symbols.For example, in an embodiment, the HEW-SIGA 1608 comprises two OFDMsymbols. In another embodiment, for example, the non-legacy portion 1603of the preamble portion 1601 includes additional OFDM symbols for theHEW signal field 1608. In some embodiments, the HEW-SIGB field 1614 isomitted.

The legacy portion 1602 of the preamble portion 1601 (i.e., L-STF,L-LTF, and L-SIG) is identical in all of the OFDM data units 1640,according to an embodiment. In another embodiment, at least the L-SIGfield is different in at least some of the OFDM data units 1640, forexample, where at least some of the OFDM data units 1640 have differentdurations. For the non-legacy portion 1603 of the preamble portion 1601(i.e., starting with HEW-SIGA), the content of the OFDM data units 1640can be variant for different client stations depending on factors suchas data rate, data quantity, configuration (e.g., number of antennas,number of supported multiple input, multiple output (MIMO) data streams,etc.) of different client stations. In some embodiments and/orscenarios, the non-legacy portion 1603 and/or the data portion 1616 aregenerated to include at least one padding OFDM symbol.

In an embodiment, the AP utilizes zero padding within the data portion1616 to ensure that each OFDM data unit 1640 has a same duration and/ornumber of OFDM symbols (i.e., the duration of the longest OFDM dataunit). In one embodiment, a MAC unit of the AP zero pads one or more MACservice data units (MSDUs) that are included in a MAC protocol data unit(MPDU), which is in turn included in a PHY protocol data unit (PPDU). Byzero padding an MSDU, for example, the lengths of the MPDU and the PPDUare increased.

In some embodiments, the AP inserts additional HEW long training fieldsinto the non-legacy portion 1603. In an embodiment, the AP generates theOFDMA data unit such that each OFDM tone block has a same number ofHEW-LTF fields. For example, in an embodiment, the AP generates theOFDMA data unit such that each OFDM data unit uses a same number ofspatial streams. In another embodiment where the number of spatialstreams are different for at least some OFDM tone blocks, the APgenerates the OFDMA data unit with additional HEW-LTF fields such thateach OFDM data unit has the same number (i.e., a maximum number) ofHEW-LTF fields.

In an embodiment, the AP determines a number of padding OFDM symbols tobe included in the OFDM data unit 1640-2 as a difference between a totalnumber of OFDM symbols of the OFDM data unit 1640-3 and a total numberof OFDM symbols of the OFDM data unit 1640-2. For example, in anembodiment, at least one of the OFDM data units 1640 (i.e., the dataunits 1640-1, 1640-2, and 1640-4) includes padding such that a totallength of the non-legacy portion 1603 and the OFDM data unit 1616 isequal to a total length of the non-legacy portion 1603 and the dataportion 1616 of the OFDM data unit 1640-3.

In another embodiment, the AP generates the OFDM data unit 1640-2 toinclude at least one padding OFDM symbol such that a sum of a number ofOFDM symbols in the non-legacy portion 1603 and a number of OFDM symbolsof the OFDM data unit 1616 of the OFDM data unit 1640-2 is equal to asum of a number of OFDM symbols of the non-legacy portion 1603 and anumber of OFDM symbols of the OFDM data unit 1616 of the OFDM data unit1640-3.

In an embodiment, the AP determines a number of OFDM symbols (N_(sym,u))for each user based on a number data bytes and an MCS value for eachuser and inserts padding OFDM symbols such that each OFDM data unit 1640has a number of symbols equal to N_(sym)=max(N_(sym,u)). In someembodiments, the AP determines the number of OFDM symbols based on thenon-legacy portion 1603 of the preamble portion 1601, for example, wherea number of HEW-LTFs in the OFDM tone blocks is different for at leastsome OFDM tone blocks (for example, due to different numbers of spatialstreams for different users of the OFDMA data unit). In one suchembodiment, the AP determines the number of OFDM symbols for each useras N_(sym,u)=N_(sym,u) (Data)+N_(sym,u) (Preamble). In anotherembodiment, the AP determines the number of OFDM symbols for each useras N_(sym,u)=N_(sym,u) (Data)+Delta_HEWLTF, where Delta_HEWLTF is numberof HEW-LTFs of a current user subtracted by the smallest number ofHEW-LTFs among all users for the OFDMA data unit 1600. In yet anotherembodiment, the AP determines the number of OFDM symbols for each useras N_(sym) (Preamble+Data)=max(N_(sym,u) (data)+N_(HEWLTF,u)). In someembodiments, the AP determines a number of data field symbols forsetting the L-LENGTH field in L-SIG 1606 as the value of N_(sym) (Data)reduced by the added number of HEWLTF symbols or the delta values. In anembodiment, the AP determines the number of padding OFDM symbols foreach client station in an uplink OFDMA data unit and sends a sync framewith the determined number of padding OFDM symbols, or another suitableindicator, to inform each client station of the PHY parameters (e.g.N_(sym)). Each client station then jointly transmits a portion of theuplink OFDMA data unit according to the PHY parameters included in thesync frame.

In some embodiments, the AP sets an OFDMA indicator (OI) 1650 in theOFDMA data unit 1600 to signal the receiver that the current data unitis a downlink OFDMA data unit. According to an embodiment, the OFDMAindicator 1650 is set to indicate one of (i) the multiple access mode or(ii) the regular mode. In an embodiment, the OFDMA indicator 1650comprises one bit, wherein a first value of the bit indicates theregular mode and a second value of the bit indicates the multiple accessmode. In some embodiments, the OFDMA indicator 1650 is combined with amodulation and coding scheme (MCS) indicator or other suitablesub-field. In an embodiment, for example, the regular mode correspondsto MCS values which are determined to be valid by a legacy receiverdevice (e.g., in compliance with IEEE 802.11ac protocol), while themultiple access mode corresponds to an MCS value that is determined tobe invalid (or not supported) by the legacy receiver device (e.g., notin compliance with IEEE 802.11ac protocol). In other embodiments, theOFDMA indicator 1650 has a plurality of bits that indicate a pluralityof regular mode MCS values and a plurality of range extension mode MCSvalues.

In an embodiment, the OFDMA indicator 1650 is a “reserved bit” in eachof the L-SIG fields which the AP sets to “1” (the IEEE 802.11a and802.11n Standards specify that the “reserved bit” in L-SIG to “0”) tosignal the receiver that the current data unit is a downlink OFDMA dataunit. Additionally, the AP sets the Length and Rate sub-fields in eachoff the L-SIG fields to correspond to T, the duration of the longestOFDM data unit 1640 and non-legacy portion 1603 (i.e., OFDM data unit1640-3). According to another embodiment, the OFDMA indicator 1650 is a“reserved bit” in each of the HEW-SIGA fields which the AP sets to “0”to signal the receiver that the current data unit is a downlink OFDMAdata unit.

In some embodiments, the OFDMA indicator 1650 includes a group IDsub-field within the HEW-SIGA 1608. In an embodiment, the group IDsub-field identifies an OFDMA group (i.e., a plurality of clientstations intended to decode the OFDMA data unit 1600). In one suchembodiment, the group ID sub-field includes a group ID value thatindicates any of a multi-user (MU) MIMO data unit, an OFDMA data unit,or a single user data unit. In this embodiment, a separate indicationfield is not needed to distinguish between OFDMA data units andnon-OFDMA data units and thus a receiver can determine which type ofdata unit by parsing the group ID sub-field. In one embodiment, thegroup ID sub-field indicates that OFDMA and MU-MIMO are used togetherwithin a same data unit.

In another embodiment, the OFDMA indicator 1650 includes both an OFDMAindication sub-field (i.e., to indicate that the data unit is an OFDMAdata unit) and a group ID sub-field (i.e., to indicate which group ofclient stations are intended to decode the data unit). In someembodiments, the OFDMA indicator 1650 also includes a user ID sub-fieldthat indicates which client station within an OFDMA group is intended todecode a corresponding OFDM tone block. In an embodiment, the OFDMAindicator 1650 is configured to signal the MCS, number of spatialstreams, a coding scheme, space time block coding, or other PHYparameters for decoding each corresponding OFDM tone block. In someembodiments, where the number of HEW-LTFs for all users in differentOFDM tone blocks are the same (i.e., insertion of HEW-LTFs for paddingor corresponding to a number for the largest N_(sts) among clientstations), the OFDMA indicator 1650 signals both the N_(sts) of thecurrent client station and a maximum N_(sts) among all client stations.

In some embodiments, the OFDMA indicator 1650 includes a tone blockassignment indication that indicates which OFDM tone blocks have beenassigned to a client station. In an embodiment, the tone blockassignment indication is a mapping table that maps a user ID to an OFDMtone block ID. In some embodiments, the OFDMA indicator 1650 isdifferent for subsequent OFDMA data units, which allows the AP todynamically partition and/or assign OFDM tone blocks to client stationson a per-data unit basis. In other embodiments, the tone blockassignment indication is omitted, for example, where the OFDM tone blockassignment is fixed for a longer duration (e.g., fixed when an OFDMAgroup is formed or changed after a predetermined number of data unitshave been sent).

In other embodiments, the AP signals that a data unit is a downlinkOFDMA data unit using techniques other than those described above. Forexample, according to one embodiment, the AP uses MAC layer signaling toreserve a time period for transmitting a downlink OFDMA data unit. Inthis embodiment, MAC layer signaling is utilized to specify the durationT of the downlink OFDMA data unit 1600. In another embodiment, MAC layersignaling does not specify the duration T of the downlink OFDMA dataunit 1600, but rather specifies different respective times at whichrespective client stations should send respective acknowledgments of thedownlink OFDMA data unit 1600. In another embodiment, the AP or clientstation utilizes MAC layer signaling to specify a single time at whichall client stations corresponding to the downlink OFDMA data unit 1600should simultaneously transmit respective acknowledgments.

In some embodiments, the L-SIG 1606 and HEW-SIGA 1608 have the samemodulation as the modulation of the corresponding field as defined inthe IEEE 802.11ac Standard. Accordingly, a first sub-field of theHEW-SIGA 1608 is modulated the same as the L-SIG field. On the otherhand, a second sub-field of the HEW-SIGA 1608 is rotated by 90 degreesas compared to the modulation of the L-SIG field. In some embodimentshaving a third sub-field of the HEW-SIGA 1608, the second sub-field ismodulated the same as the L-SIG field and the first sub-field, while thethird sub-field is rotated by 90 degrees as compared to the modulationof the L-SIG field, the first sub-field, and the second sub-field.

In an embodiment, because the modulations of the L-SIG 1606 andsub-fields of the HEW-SIGA 1608 of the OFDM data unit 1640 correspond tothe modulations of the corresponding fields in a data unit that conformsto the IEEE 802.11ac Standard (e.g., the data unit 500 of FIG. 5),legacy client stations configured to operate according to the IEEE802.11a Standard and/or the IEEE 802.11n Standard will assume, in atleast some circumstances, that the OFDM data unit 1640 conforms to theIEEE 802.11ac Standard and will process the OFDM data unit 1640accordingly. For example, a client station that conforms to the IEEE802.11a Standard will recognize the legacy IEEE 802.11a Standard portionof the preamble of the data unit 1640 and will set a duration of thedata unit (or the data unit duration) according to a duration indicatedin the L-SIG 1606. For example, the legacy client station 25-4 willcalculate a duration for the data unit based on a rate and a length(e.g., in number of bytes) indicated in the L-SIG field 1606, accordingto an embodiment. In an embodiment, the rate and the length in the L-SIGfield 1606 are set such that a client station configured to operateaccording to a legacy communication protocol will calculate, based therate and the length, a packet duration (T) that corresponds to, or atleast approximates, the actual duration of the data unit 1640. Forexample, the rate is set to indicate a lowest rate defined by the IEEE802.11a Standard (i.e., 6 Mbps), and the length is set to a valuecomputed such that packet duration computed using the lowest rate atleast approximates the actual duration of the data unit 1640, in oneembodiment.

In an embodiment, a legacy client station that conforms to the IEEE802.11a Standard, when receiving the data unit 1640, will compute apacket duration for the data unit 1640, e.g., using a rate field and alength field of L-SIG field 1606, and will wait until the end of thecomputed packet duration before performing clear channel assessment(CCA), in an embodiment. Thus, in this embodiment, communication mediumis protected against access by the legacy client station at least forthe duration of the data unit 1640. In an embodiment, the legacy clientstation will continue decoding the data unit 1640, but will fail anerror check (e.g., using a frame check sequence (FCS)) at the end of thedata unit 1640.

Similarly, a legacy client station configured to operate according tothe IEEE 802.11n Standard, when receiving the data unit 1640, willcompute a packet duration (T) of the data unit 1640 based on the rateand the length indicated in the L-SIG 1606 of the data unit 1640, in anembodiment. The legacy client station will detect the modulation of thefirst sub-field of the HEW signal field (HEW-SIGA) as BPSK and willassume that the data unit 1640 is a legacy data unit that conforms tothe IEEE 802.11a Standard. In an embodiment, the legacy client stationwill continue decoding the data unit 1640, but will fail an error check(e.g., using a frame check sequence (FCS)) at the end of the data unit.In any event, according to the IEEE 802.11n Standard, the legacy clientstation will wait until the end of a computed packet duration (T) beforeperforming clear channel assessment (CCA), in an embodiment. Thus,communication medium will be protected from access by the legacy clientstation for the duration of the data unit 1640, in an embedment.

A legacy client station configured to operate according to the IEEE802.11ac Standard but not the first communication protocol, whenreceiving the data unit 1640, will compute a packet duration (T) of thedata unit 1640 based on the rate and the length indicated in the L-SIG1606 of the data unit 1640, in an embodiment. However, the legacy clientstation will not be able to detect, based on the modulation of the dataunit 1640, that the data unit 1640 does not conform to the IEEE 802.11acStandard, in an embodiment. In some embodiments, one or more sub-fieldsof the HEW signal field 1608 of the data unit 1640 is/are formatted tointentionally cause the legacy client station to detect an error whendecoding the data unit 1640, and to therefore stop decoding (or “drop”)the data unit 1640. For example, HEW-SIGA 1608 of the data unit 1640 isformatted to intentionally cause an error when the SIGA field is decodedby a legacy device according to the IEEE 802.11ac Standard, in anembodiment. Further, according to the IEEE 802.11ac Standard, when anerror is detected in decoding the VHT-SIGA field, the client stationwill drop the data unit 1640 and will wait until the end of a computedpacket duration (T), calculated, for example, based on a rate and alength indicated in the L-SIG 1606 of the data unit 1640, beforeperforming clear channel assessment (CCA), in an embodiment. Thus,communication medium will be protected from access by the legacy clientstation for the duration of the OFDM data unit 1640, in an embodiment.

In some embodiments, a different preamble format is used for themultiple access mode data units as compared to the preamble used forregular mode data units. In such embodiments, a device receiving a dataunit can automatically detect whether the data unit is a regular modedata unit or a multiple access mode data unit based on the format of thepreamble of the data unit. FIG. 17A is a diagram illustrating a regularmode data unit 1700, according to an embodiment. The regular mode dataunit 1700 includes a regular mode preamble 1701. The regular modepreamble 1701 is generally the same as the preamble 1601 of the OFDMdata units 1640 of FIG. 16. In an embodiment, the preamble 1701 includesa HEW-SIGA field 1708, which includes a first HEW-SIGA1 field 1708-1 anda second first HEW-SIGA2 field 1708-1. In an embodiment, the HEW-SIGAfield 1708 (e.g., the HEW-SIGA1 1708-1 or the HEW-SIGA2 1708-2) of thepreamble 1701 includes an OFDMA indication 1702. The OFDMA indication1702 is set to indicate whether the multiple access mode or the regularmode is used for the data unit 1700, in an embodiment. In an embodiment,the OFDMA indication 1702 comprises one bit, wherein a first value ofthe bit indicates the regular mode and a second value of the bitindicates the multiple access mode. As will be explained in more detailbelow, a device receiving the data unit 1700 is able to detect, based onthe format of the preamble 1701, that the preamble 1701 is a regularmode preamble, and not a multiple access mode preamble, in anembodiment. Upon detecting that the preamble 1701 is the regular modepreamble, the receiving device determines, based on the OFDMA indication1702, whether the multiple access mode or the regular mode is used forOFDM symbols of the data portion 1616, and decodes the data portion 1616accordingly, in an embodiment. In some embodiments, when the OFDMAindication 1702 indicates that the multiple access mode is beingutilized, the OFDM symbols of a portion of the preamble 1701 (e.g., theHEW-LTFs and HEW-SIGB), as well as OFDM symbols of the data portion 1616are generated using OFDM modulation with smaller tone spacing comparedto tone spacing used for regular mode OFDM symbols.

FIG. 17B is a diagram illustrating a multiple access mode data unit1750, according to an embodiment. The multiple access mode data unit1750 includes a multiple access mode preamble 1751. The data unit 1750is generally similar to the data unit 1700 of FIG. 17A, except that thepreamble 1751 of the data unit 1750 is formatted differently from thepreamble 1701 of the data unit 1700. In an embodiment, the preamble 1751is formatted such that a receiving device that operates according to theHEW communication protocol is able to determine that the preamble 1751is a multiple access mode preamble rather than a regular mode preamble.In an embodiment, the multiple access mode preamble 1751 includes anL-STF 1604, an L-LTF 1605, and an L-SIG 1606, and one or more first HEWsignal fields (HEW-SIGAs) 1752. In an embodiment, the preamble 1750further includes one or more secondary L-SIG(s) 1754 that follow theL-SIG field 1606. The secondary L-SIG(s) 1754 are followed by a secondL-LTF field (L-LTF2) 1756, in some embodiments. In other embodiments,the preamble 1751 omits the L-SIG(s) 1754 and/or the L-LTF2 1756. Insome embodiments, the preamble 1751 also includes an HEW-STF 1758, oneor more HEW-LTF fields 1760, and a second HEW signal field (HEW-SIGB)1762. In other embodiments, the preamble 1751 omits the HEW-STF 1758,the HEW-LTF(s) 1760 and/or the HEW-SIGB 1762. In an embodiment, the dataunit 1750 also includes a data portion 1616 (not shown in FIG. 17B). Insome embodiments, the HEW signal fields (HEW-SIGAs) 1752 are modulatedusing a same multiple access mode as the data field 1616.

In an embodiment, one or more symbols of the HEW-SIGAs 1752 is modulatedusing QBPSK instead of BPSK, for example, to allow autodetection betweenthe regular mode and the multiple access mode by the receiving devicethat operates according to the HEW communication protocol. In anembodiment, for example, where the regular mode preamble includes twoBPSK symbols and one Q-BPSK symbol after the L-SIG 1606 field, themultiple access mode preamble includes three BPSK symbols and one Q-BPSKsymbol after the L-SIG 1606 field. In some embodiments, for example,where autodetection differentiates the regular mode from the multipleaccess mode, some bits are omitted from the HEW-SIGAs 1752, such as bitsused to indicate signal bandwidth, MCS value, or other suitable bits.

In one embodiment in which the preamble 1751 includes one or moresecondary L-SIG(s) 1754, the content of each of the L-SIG(s) 1754 is thesame as the content of the L-SIG 1606 of the data unit 1750. In anembodiment, a receiving device receiving the data unit 1750 determinesthat the preamble 1751 corresponds to a multiple access mode preamble bydetecting the repetition(s) of the L-SIG fields 1606, 1754. Further, inan embodiment, both a rate subfield and a length subfield of the L-SIG1606, and, accordingly, the rate subfield(s) and the length subfield(s)of the secondary L-SIG(s) 1754 are set to fixed (e.g., predetermined)values. In this case, upon detecting the repetition(s) of the L-SIGfields 1606, 1754, the receiving device uses the fixed values in therepeating L-SIG fields as additional training information to improvechannel estimation, in an embodiment. In some embodiments, however, atleast the length subfield of the L-SIG 1606, and accordingly at leastthe length fields of the secondary L-SIG(s) 1754, is not set to a fixedvalue. For example, the length field is instead set to a valuedetermined based on the actual length of the data unit 1750, in anembodiment. In one such embodiment, the receiving device first decodesthe L-SIG 1606, and then detects the repetition(s) of the L-SIG fields1606, 1754 using the value of the length subfield in L-SIG 1606. Inanother embodiment, the receiving device first detects the repetition(s)of the L-SIG fields 1606, 1754, and then combines the detected multipleL-SIG fields 1606, 1754 to improve decoding reliability of the L-SIGfields 1606, 1754 and/or uses the redundant information in the multipleL-SIG fields 1606, 1754 to improve channel estimation.

In an embodiment in which the preamble 1751 includes L-LTF2 1756, theOFDM symbol(s) of the L-LTF2 1756 are generated using the multipleaccess mode. In another embodiment in which the preamble 1751 includesL-LTF2 1756, the OFDM symbol(s) of the L-LTF2 1756 are generated usingthe regular mode. For example, if a double guard interval (DGI) used inthe L-LTF 1605 is sufficiently long for the communication channel inwhich the data unit 1750 travels from the transmitting device to thereceiving device, then OFDM symbols of the L-LTF2 1756 are generatedusing the regular mode or, alternatively, the preamble 1751 omits theL-LTF2 1756, in an embodiment.

In another embodiment, the preamble 1751 omits the secondary L-SIG(s)1754, but includes the L-LTF2 1756. In this embodiment, a receivingdevice detects that the preamble 1751 is the multiple access modepreamble by detecting the presence of the L-LTF2 1756. FIGS. 18A-18B arediagrams illustrating two possible formats of LTFs suitable for use asthe L-LTF2 1756 according to two example embodiments. Turning first toFIG. 18A, in a first example embodiment, an L-LTF2 1800 is formatted inthe same manner as the L-LTF 1605, i.e., as defined by a legacycommunication protocol (e.g., the IEEE 802.11a/n/ac Standards). Inparticular, in the illustrated embodiment, the L-LTF2 1800 includes adouble guard interval (DGI) 1802 followed by two repetitions of a longtraining sequence 1804, 1806. Turning now to FIG. 18B, in anotherexample embodiment, an L-LTF2 1808 is formatted differently from theL-LTF 1605. In particular, in the illustrated embodiment, the L-LTF21808 includes a first normal guard interval 1810, a first repetition ofa long training sequence 1812, a second normal guard interval 1814, anda second repetition of the long training sequence 1816.

Referring back to FIG. 17B, in an embodiment, the HEW-SIGA(s) 1752 aregenerated using the multiple access mode. In an embodiment, the numberof the HEW-SIGAs 1752 is the same as the number of the HEW-SIGA(s) 1708of the regular mode preamble 1701. Similarly, in an embodiment, thecontent of the HEW-SIGAs 1752 is the same as the content of theHEW-SIGA(s) 1708 of the regular mode preamble 1701. In otherembodiments, the number and/or the content of the HEW-SIGAs 1752 isdifferent from the number and/or content of the HEW-SIGA(s) 1708 of theregular mode preamble 1701. A device receiving the data unit 1750decodes the HEW-SIGA(s) 1752 using the multiple access mode based ondetecting that the preamble 1751 corresponds to the multiple access modepreamble and interprets the HEW-SIGA(s) 1752 appropriately as definedfor the multiple access mode, in an embodiment.

In an embodiment in which the preamble 1751 omits the L-SIG(s) 1754and/or L-LTF2 1756, a receiving device determines whether a preamblecorresponds to the multiple access mode preamble 1751 or to the normalmode preamble 1701 by detecting whether the HEW-SIGA field in thepreamble is generated using the multiple access mode or the regular modebased on auto-correlation of the HEW-SIGA field using the multipleaccess mode and the regular mode. FIGS. 19A-19B are diagrams of theHEW-SIGA 1708 of the regular mode preamble 1701 and the HEW-SIGA 1752 ofthe multiple access mode preamble 1751, respectively, according to anembodiment. In the illustrated embodiment, the HEW-SIGA 1708 of theregular mode preamble 1701 includes a first NGI 1902, a first HEW-SIGAfield 1904, a second NGI 1906, and a second HEW-SIGA field 1908. On theother hand, the HEW-SIGA 1752 of the multiple access mode preamble 1751includes a first LGI 1910, a first HEW-SIGA field 1912, a second LGI1914, and a second HEW-SIGA field 1916. In an embodiment, a receivingdevice performs a first auto-correlation of the HEW-SIGA field using anormal guard interval structure, such as the structure illustrated inFIG. 19A, performs a second auto-correlation using a long guard intervalstructure, such as the structure illustrated in FIG. 19B, and performs acomparison of the auto-correlation results. If auto-correlation of theHEW-SIGA field using the long guard interval produces a greater resultcompared to the result of the auto-correlation of the HEW-SIGA fieldusing the normal guard interval, then the receiving device determinesthat the preamble corresponds to the multiple access mode preamble 1751,in an embodiment. On the other hand, if auto-correlation of the HEW-SIGAfield using the normal guard interval produces a greater result comparedto the result of auto-correlation of the HEW-SIGA field with the longguard interval, then the receiving device determines that the preamblecorresponds to the regular mode preamble 1701, in an embodiment.

Referring again to FIG. 17B, in an embodiment, the preamble 1751 isformatted such that a legacy client station can determine a duration ofthe data unit 1750 and/or that the data unit does not conform to alegacy communication protocol. Additionally, the preamble 1751 isformatted such that a client station that operates according to the HEWprotocol is able to determine that the data unit conforms to the HEWcommunication protocol, in an embodiment. For example, at least two OFDMsymbols immediately following the L-SIG 1606 of the preamble 1751, suchas the L-SIG(s) 1754 and/or the L-LTF2 1756 and/or the HEW-SIGA(s) 1752,are modulated using BPSK modulation. In this case, a legacy clientstation will treat the data unit 1750 as a legacy data unit, willdetermine a duration of the data unit based on the L-SIG 1606, and willrefrain from accessing the medium for the determined duration, in anembodiment. Further, one or more other OFDM symbols of the preamble1751, such as one or more of the HEW-SIG(s) 1752 are modulated usingQ-BPSK modulation, allowing a client station operating according to theHEW communication protocol to detect that the data unit 1750 conforms tothe HEW communication protocol, in an embodiment.

In some embodiments, the HEW communication protocol allows beamformingand/or multi user MIMO (MU-MIMO) transmission. With continued referenceto FIG. 17B, in an embodiment in which the preamble 1751 includes theHEW-STF 1758 and the HEW-LTF(s) 1760, the AP 14 applies beamformingand/or multi-user transmission beginning with the HEW-STF 1758. In otherwords, the fields of the preamble 1751 precede the HEW-STF 1758 areomni-directional and, in multi-user mode, are intended to be received byall intended recipients of the data unit 1750, while the HEW-STF field1758, as well as the preamble fields that follow the HEW-STF field 1758and the data portion that follows the preamble 1751, are beam-formedand/or include different portions intended to be received by differentintended recipients of the data unit 1750, in an embodiment. In anembodiment, the HEW-SIGB field 1762 includes user-specific informationfor the intended recipients of the data unit 1750 in MU-MIMO mode. TheHEW-SIGB field 1762 is generated using the regular mode or the multipleaccess mode, depending on an embodiment. Similarly, the HEW-STF 1758 isgenerated using the regular mode or the multiple access mode, dependingon an embodiment. In an embodiment, the training sequence used on theHEW-STF 1758 is the sequence defined in a legacy communication protocol,such as in the IEEE 802.11ac protocol.

In some embodiments, a receiver device uses the HEW-STF field 1758 tore-start an automatic gain control (AGC) process for receiving the dataportion 716. The HEW-STF has a same duration as the VHT-STF (i.e., 4microseconds), in an embodiment. In other embodiments, the HEW-STF has alonger duration than the VHT-STF. In an embodiment, the HEW-STF has asame time-domain periodicity as the VHT-STF, such that in the frequencydomain there are one non-zero tones every 4 tones and using a same tonespacing as IEEE 802.11ac. In other embodiments having a 1/N tonespacing, the HEW-STF has one non-zero tone in every 4*N tones. Inembodiments where the overall bandwidth for the data unit is greaterthan 20 MHz, (e.g., 40 MHz, 80 MHz, etc.), the HEW-STF uses the samewider bandwidth VHT-STF as in IEEE 802.11ac (i.e., a duplication of the20 MHz VHT-STF for overall bandwidth of 40 MHz, 80 MHz, 160 MHz, etc.).

FIG. 20A is a block diagram illustrating a multiple access mode dataunit 2000, according to an embodiment. The data unit 2000 includes amultiple access mode preamble 2001. The multiple access mode preamble2001 is generally similar to the multiple access mode preamble 1751 ofFIG. 17B, except that the L-SIG 1606 and the secondary L-SIG 1754 of thepreamble 1751 are combined into a single L-SIG field 2006 in thepreamble 2001. FIG. 20B is a diagram illustrating the L-SIG field 2006according to one embodiment. In the embodiment of FIG. 20B, the L-SIGfield 2006 includes a double guard interval 2010, a first L-SIG field2012, which includes contents of L-SIG field 1606 of the preamble 1751,and a second L-SIG field 2014, which includes contents of the secondaryL-SIG2 field 1754 of the preamble 1751. In various embodiments, L-SIGfield 2006 includes a length subfield set to a fixed value or set to avariable value, as discussed above with respect to the L-SIG fields1606, 1754 of FIG. 17B. In various embodiments, redundant (repeated)bits in L-SIG field 2006 are used for improved channel estimation asdiscussed above with respect to L-SIG fields 1606, 1754 of FIG. 17B.

In an embodiment, a legacy client station receiving the data unit 2000assumes that the L-SIG field 2006 includes a normal guard interval. Asillustrated in FIG. 20C, the FFT window for L-SIG information bitsassumed at the legacy client station is shifted compared to the actualL-SIG field 2012, in this embodiment. In an embodiment, to ensure thatconstellation points within the FFT window correspond to BPSKmodulation, as expected by the legacy client station, and thus to allowthe legacy client station to properly decode the L-SIG field 2012,modulation of the L-SIG field 2012 is phase-shifted relative to regularBPSK modulation. For example, in a 20 MHz OFDM symbol, if the normalguard interval is 0.8 μs, and the double guard interval is 1.6 μs, thenmodulation of an OFDM tone k of the L-SIG field 2012 is shifted withrespect to the corresponding OFDM tone k of the original L-SIG as can beseen from:

S _(LSIG) ^((k)) =S _(SLSIG-LSIG) ^((k)) e ^(−j·2π·0.8·20/64) =S_(SLSIG-LSIG) ^((k))·(−j)  (Equation 1)

Accordingly, in an embodiment, L-SIG field 2012 is modulated usingreverse Q-BPSK rather than regular BPSK. Thus, for example, a bit ofvalue 1 is modulated onto −j, and a bit of value 0 is modulated onto j,resulting in {j, −j} modulation rather than the regular {1, −1} BPSKmodulation, in an embodiment. In an embodiment, due to the reverseQ-BPSK modulation of the L-SIG field 2012, a legacy client station canproperly decode the L-SIG field 2012 and determine the duration of thedata unit 2000 based on the L-SIG 2012 field, in an embodiment. A clientstation that operates according to the HEW protocol, on the other hand,can auto-detect that the preamble 2001 is a multiple access modepreamble by detecting the repetition of the L-SIG field 2012 or bydetecting the reverse Q-BPSK modulation of the L-SIG field within theFFT window of the legacy client station, in an embodiment.Alternatively, in other embodiments, a client station that operatesaccording to the HEW protocol detects that the preamble 2001 is amultiple access mode preamble using other detection methods discussedabove, such as based on modulation or format of the HEW-SIGA field(s)1752.

Referring FIGS. 17A-17B and 20A, long guard interval is used for initialOFDM symbols of both a regular mode preamble (e.g., the preamble 1701)and a multiple access mode preamble (e.g., the preamble 1751 or thepreamble 2001), in some embodiments. For example, referring to FIGS.17A-17B, the L-STF field 1604, the L-LTF field 1605 and the L-SIG field1606, 1754, and HEW-SIGA field 1752 is each generated using the longguard interval, in an embodiment. Similarly, referring to FIG. 20A, theL-STF field 1604, the L-LTF field 1605, the L-SIG field 2006, and theHEW-SIGA(s) 1752 are generated using the long guard interval, in anembodiment. In an embodiment, a receiving device can determine whether apreamble corresponds to the regular mode preamble or the multiple accessmode preamble based on modulation of the HEW-SIGA field 1752 (e.g.,Q-BPSK) or based on an indication included in the HEW-SIGA field 1752,in various embodiments. Further, similar to the preamble 1751 of FIG.17B, the preamble 2001 of FIG. 20A includes or omits the second L-LTF2field 1756, depending on the embodiment and/or scenario.

FIG. 21 is a block diagram illustrating a format of an HEW-SIGA field2100, according to an embodiment. In some embodiments, the HEW-SIGAfield(s) 1752 of the data unit 1750 or the data unit 2000 are formattedas the HEW-SIGA field 2100. In some embodiments, the HEW-SIGA field(s)1708 are formatted as the HEW-SIGA field 2100. The HEW-SIGA field 2100includes a double guard interval 2102, a first repetition of a HEW-SIGAfield 2104 and a second repetition of a HEW-SIGA field 2106. In anexample embodiment, the DGI is 1.8 μs and each repetition of HEW-SIGA is3.2 μs. In an embodiment, the repeated bits in the HEW-SIGA field 2100are used to increase reliability of decoding of the HEW-SIGA field 2100.In an embodiment, the format of the HEW-SIGA field 2100 is used toauto-detect a multiple access mode preamble based on a comparisonbetween auto-correlation of the HEW-SIGA field of the preamble using theformat of the HEW-SIGA field 2100 and auto-correlation of the HEW-SIGAfield of the preamble using the regular HEW-SIGA field format used inthe regular mode.

FIG. 22 is a block diagram of an example downlink OFDMA data unit 2200,according to another embodiment. In FIG. 22, an 80 MHz communicationchannel is partitioned into four contiguous OFDM tone blocks 2241, 2242,2243, and 2244, according to an embodiment. The OFDM tone block 2241 andOFDM tone block 2242 are adjacent and each have a bandwidth of 10 MHz,thus together the OFDM tone block 2241 and OFDM tone block 2242 span abandwidth equal to a smallest channel bandwidth of a legacy WLANcommunication protocol (i.e., a legacy tone block of 20 MHz). The OFDMtone block 2243 has a bandwidth of 20 MHz. The OFDM tone block 2244spans a bandwidth of 40 MHz. The OFDM tone blocks 2242 and 2244 areassigned to, and include independent data streams for, two clientstations STA 2 and STA 3, respectively. The OFDM tone blocks 2241 and2243, which are separated in frequency by the OFDM tone block 2242, areassigned to and include portions of a data stream for client station STA1 and use a channel bonding technique, as described herein.

The OFDMA data unit 2200, and thus each OFDM data unit 2241, 2242, 2243,and 2244, includes a preamble portion 2201 and a data portion 1616(e.g., a data field for the corresponding client station), in anembodiment. In other embodiments, at least some of the OFDM data unitsomit the data portion 1616. The preamble portion 2201 of each OFDM dataunit includes at least a legacy portion 2202 and a non-legacy portion2203, in an embodiment. The legacy portion 2202 and non-legacy portion2203 are generally the same as the legacy portion 1602 and non-legacyportion 1603, respectively, of the OFDM data units 1640 of FIG. 16.

In an embodiment, each 20 MHz sub-band (i.e., a legacy tone block) ofthe communication channel includes a legacy portion 2202 having an L-STF1604, L-LTF 1605, and L-SIG 1606 such that a legacy client station canproperly decode the L-SIG field 1606 for the 20 MHz sub-band. In theembodiment of FIG. 22, a first legacy tone block 2261 spans the OFDMtone blocks 2241 and 2242, a second legacy tone block 2262 spans theOFDM tone block 2243, a third legacy tone block 2263 spans a portion2244-1 of the OFDM tone block 2244, and a fourth legacy tone block 2264spans a portion 2244-2 of the OFDM tone block 2244. In an embodiment,the legacy portion 2202 of the OFDM data units 2241 and 2242 span a same20 MHz sub-band (i.e., the legacy tone block 2261) and thus overlap infrequency. In this embodiment, the OFDM data units 2241 and 2242 use asame legacy portion 2202.

The L-SIG field 1606 corresponding to each legacy tone block 2261, 2262,2263, and 2264 indicates a duration for OFDM data units within therespective legacy tone block, in an embodiment. In some embodiments, theL-SIG fields 1606 corresponding to each legacy tone block of the OFDMAdata unit 2200 have identical values, for example, where thecorresponding OFDM data units have a same duration (e.g., due to OFDMsymbol padding). In other embodiments, the L-SIG fields 1606 of thelegacy tone blocks have at least some different values. In an embodimentwhere channel bonding is used and a client station is assigned multipleOFDM tone blocks, the L-SIG fields corresponding to different 20 MHzsub-bands that contain the OFDM tone blocks assigned to the same clientstation have a same L-LENGTH value such that each L-LENGTH value decodedby the client station indicates a same packet duration. For example, inthe embodiment of FIG. 22, an L-LENGTH value of the L-SIG field 1606 ofOFDM data units 2241 and 2243 indicate a same value.

In some embodiments, at least the legacy portion 2202 of the legacy toneblocks 2261, 2262, 2263, and 2264 is modulated using a legacy tone plan.In an embodiment, the non-legacy portion 2203 and data portion 1616 ofat least one OFDM tone block of the OFDMA data unit 2200 are modulatedusing a non-legacy tone plan (i.e., a tone plan different from thelegacy tone plan). For example, in an embodiment, the non-legacy portion2203 and data portion 1616 corresponding to an OFDM tone block thatspans a bandwidth smaller than 20 MHz is modulated using a non-legacytone plan. In the embodiment of FIG. 22, the OFDM tone block 2241 andthe OFDM tone block 2242 each span a bandwidth of 10 MHz and thus thecorresponding non-legacy portions 2203 and data portions 1616 aremodulated using a non-legacy tone plan, such as the tone plan 800described with respect to FIG. 8. In other embodiments, the legacyportion 2202 and non-legacy portion 2203 are modulated using the legacytone plan while the data portion 1616 is modulated using the non-legacytone plan. In an embodiment, at least some OFDM symbols of the HEW-SIGAfield 1608 of the non-legacy portion 2203 are modulated using the legacytone plan and thus the HEW-SIGA field 1608 is shared by the OFDM dataunits corresponding to the OFDM tone blocks 2241 and 2242.

FIG. 23 is a block diagram of an example downlink OFDMA data unit 2300using reduced tone spacing, according to an embodiment. The tone spacingis a spacing between sub-carrier frequencies of the OFDM tone block. TheOFDMA data unit 2300 is generally the same as the OFDMA data unit 2200,however at least some OFDM tone blocks use a reduced tone spacing for atleast a portion of the corresponding OFDM data unit, in an embodiment.In the embodiment of FIG. 23, a first OFDM tone block 2341 and a secondOFDM tone block 2342 (in place of the OFDM tone block 2241 and OFDM toneblock 2242) use a reduced tone spacing. In other embodiments, the OFDMAdata unit 2300 uses a reduced tone spacing for each OFDM tone block forat least a portion of the OFDMA data unit 2300.

In the embodiment of FIG. 23, a first legacy tone block 2361 spans theOFDM tone block 2341 and the OFDM tone block 2342. In some embodiments,at least the legacy portion 2202 of the legacy tone blocks 2361, 2362,2263, and 2264 is modulated using a legacy tone spacing (i.e., a spacingof 312.5 kHz between tones), for example, according to IEEE 802.11ac. Inan embodiment, the non-legacy portion 2203 and data portion 1616 of atleast one OFDM tone block of the OFDMA data unit 2200 are modulatedusing a reduced tone spacing as compared to the legacy tone spacing. Inan embodiment, at least some OFDM symbols of the non-legacy portion2203, such as the HEW-SIGA field 1608 and/or HEW-STF 1610, are modulatedusing the legacy tone spacing and thus the HEW-SIGA field 1608 is sharedby the OFDM data units corresponding to the OFDM tone block 2341 and theOFDM tone block 2242. In some embodiments, the OFDM data unitscorresponding to the OFDM tone block 2341 and 2342 use a non-legacy toneplan, as described above with respect to FIG. 22, in combination withthe non-legacy tone spacing.

In some embodiments, for example, whereas the regular mode for a legacytone block (i.e., 20 MHz) uses a 64-point discrete Fourier transform(DFT), resulting in 64 OFDM tones (e.g., tone indices −32 to +31), atleast some OFDM tone blocks in the OFDMA data unit 2300 use a 128-pointDFT for at least some OFDM symbols in the legacy tone block, resultingin 128 OFDM tones (e.g., indices −64 to +63) in the same bandwidth. Inthis case, tone spacing is reduced by a factor of two (½) compared toregular mode OFDM symbols while using a same tone plan. As anotherexample, whereas the regular mode for a legacy tone block uses a64-point discrete Fourier transform (DFT) resulting in 64 OFDM tones,the OFDMA data unit 2300 uses a 256-point DFT for at least some OFDMsymbols in the legacy tone block resulting in 256 OFDM tones in the samebandwidth. In this case, tone spacing is reduced by a factor of four (¼)compared to the regular mode OFDM symbols. In such embodiments, longguard interval durations of, for example, 1.6 μs is used. However, theduration of the information portion of the multiple access mode OFDMsymbol is increased (e.g., from 3.2 μs to 6.4 μs), and the percentage ofthe guard interval portion duration to the total OFDM symbols durationremains the same, in an embodiment. Thus, in this case, loss ofefficiency due to a longer guard interval symbol is avoided, in at leastsome embodiments. In various embodiments, the term “long guard interval”as used herein encompasses an increased duration of a guard interval aswell as a decreased OFDM tone spacing that effectively increasesduration of the guard interval. In other embodiments, other multiplessuch as 4×, 8×, or other suitable values are used for reduced tonespacing.

In some embodiments, the OFDMA data unit 2300 uses the reduced tonespacing in combination with a range extension mode. In an embodiment,the range extension mode is used with communication channelscharacterized by relatively longer channel delay spreads (e.g., outdoorcommunication channels) or generally lower SNR values. In an embodiment,the range extension mode corresponds to a range extension coding scheme(e.g., block encoding, bit-wise replication, or symbol replication), asignal modulation scheme (e.g., phase shift keying or quadratureamplitude modulation), or both a range extension coding scheme andsignal modulation scheme. The range extension mode is configured toincrease a range and/or reduce a signal-to-noise (SNR) ratio, ascompared to the second mode (e.g., a regular mode using a regular codingscheme), at which successful decoding of PHY data units conforming tothe range extension mode is performed. In various embodiments, the rangeextension mode reduces a data rate of transmission as compared to theregular mode to achieve successful decoding with increased range and/orreduced SNR ratio.

The OFDMA data unit 2300 supports any of the regular mode, the multipleaccess mode, and the range extension mode, in some embodiments. In anembodiment, the OFDMA data unit 2300 supports any of the regular mode,the multiple access mode, the range extension mode, and the rangeextension mode in combination with the multiple access mode. In anembodiment, at least some modes supported by the OFDMA data unit 2300are indicated to a receiving device by a mode indicator, such as theOFDMA indicator 1650 as described above with respect to FIG. 16. Inanother embodiment, at least some modes are indicated to the receivingdevice by a different format of the preamble portion 2201, as describedabove with respect to FIG. 17A, 17B, 18A, 18B, 19A, 19B, 20A, 20B, 20C,or 21.

FIG. 24 is a block diagram of an example uplink OFDMA data unit 2400,according to an embodiment. The OFDMA data unit 2400 is generally thesame as the OFDMA data unit 2200, however a first portion 2451 of theOFDMA data unit 2400 is generated and transmitted by a first clientstation and a second portion 2452 of the OFDMA data unit 2400 isgenerated and transmitted by a second client station for receipt by anaccess point, in an embodiment. In some embodiments, the OFDMA indicator1650 and/or other sub-fields within the HEW-SIGA field 1608 are omitted,for example, where the AP has already determined corresponding PHYparameters.

In the embodiment shown in FIG. 24, a communication channel spans alegacy tone block 2461 (i.e., 20 MHz) and is partitioned into twocontiguous OFDM tone blocks 2441 and 2442, each spanning a sub-band of10 MHz. The OFDM tone block 2441 is assigned (i.e., by the AP 14) to andincludes portions of a data stream from a client station STA 1 (e.g.,client 25-1) and the OFDM tone block 2442 is assigned to and includesportions of a data stream from a client station STA 2 (e.g., client25-2), in an embodiment. For example, in an embodiment, the client 25-1and client 25-2 are members of an OFDMA group, as described above withrespect to FIG. 16. In other embodiments, the communication channel hasa bandwidth of 40 MHz, 80 MHz, 160 MHz, or other suitable bandwidth andis partitioned for a suitable number of client stations, as describedabove with respect to FIG. 7A, 7B, 7C, 9A, 9B, 14A, or 14B.

In an embodiment, each client station of the OFDMA group determines acorresponding assigned OFDM tone block. In some embodiments, the clientstation determines the corresponding assigned OFDM tone block based on async frame received from the AP 14 that includes PHY parameters, such asan indication of which OFDM tone blocks are assigned to a particularclient station. In an embodiment, each client station of the OFDMA grouptransmits the corresponding portion of the OFDMA data unit 2400 after ashort interframe space (SIFS) following receipt of the sync frame.

FIG. 25A is a block diagram of an example uplink OFDM data unit portion,such as the first portion 2451 of the OFDMA data unit 2400. In someembodiments, the client station 25-1 includes a PHY processing unit,such as the PHY processing units 1000, 1100, 1200, 1300, 1500, and/or1550 described above with respect to FIGS. 10, 11, 12, 13, 14A, 14B,15A, and 15B, for generating and transmitting the first portion 2451 ofthe OFDMA data unit 2400. FIG. 25B is a block diagram of another exampleuplink OFDM data unit portion, such as the second portion 1452 of theOFDMA data unit 2400, according to an embodiment. In some embodiments,the client station 25-2 includes a PHY processing unit, such as the PHYprocessing units 1000, 1100, 1200, 1300, 1500, and/or 1550 describedabove with respect to FIGS. 10, 11, 12, 13, 14A, 14B, 15A, and 15B, forgenerating and transmitting the second portion 2452 of the OFDMA dataunit 2400.

In some embodiments, the client station 25-1 generates the first portion2451 for transmission on the communication channel using data tones andpilot tones within the first OFDM tone block 2441 and the client station25-2 generates the second portion 2452 for transmission on thecommunication channel using data tones and pilot tones within the secondOFDM tone block 2442. In an embodiment, the client station 25-1generates and transmits the first portion 2451 using data tones andpilot tones within the first OFDM tone block 2441 and the second OFDMtone block 2442. For example, in an embodiment, the client station 25-1generates and transmits the legacy portion 2402 using the first OFDMtone block 2441 and the second OFDM tone block 2442 and generates andtransmits the non-legacy portion 2403 and the data portion 1616 usingonly the first OFDM tone block 2441. In an embodiment, the clientstation 25-2 generates and transmits the second portion 2452 using datatones and pilot tones within the first OFDM tone block 2441 and thesecond OFDM tone block 2442. For example, in an embodiment, the clientstation 25-2 generates and transmits the legacy portion 2402 using thefirst OFDM tone block 2441 and the second OFDM tone block 2442 andgenerates and transmits the non-legacy portion 2403 and the data portion1616 using only the second OFDM tone block 2442.

Each of the first portion 2451 and second portion 2452 include a legacyportion 2402 that spans both the first OFDM tone block 2441 and thesecond OFDM tone block 2442 and thus overlap in frequency, in anembodiment. In an embodiment, the legacy portions 2402 of the firstportion 2451 and the second portion 2452 are identical such that the AP14 receives a substantially same signal when the client station 25-1 andclient station 25-2 transmit the respective legacy portions 2402. Thenon-legacy preamble 2403 and data portion 1616 of the first portion 1451span only the first OFDM tone block 2441 and the non-legacy preamble2403 and data portion 1616 of the second portion 1452 span only thesecond OFDM tone block 2442 and thus do not overlap in frequency, in anembodiment.

In an embodiment, the client station 25-1 is configured to transmit thelegacy portion 2402, the non-legacy portion 2403, and the data portion1616 with a same per-tone transmission power. In one such embodiment, atotal power of the legacy portion 2402 is approximately two times atotal power of the non-legacy portion 2403 and the data portion 1616. Insome embodiments, the client station 25-1 is configured to transmit thelegacy portion 2402, the non-legacy portion 2403, and the data portion1616 with a same total transmission power. In one such an embodiment,the per-tone power of the non-legacy portion 2403 and the data portion1616 is approximately two times the per-tone power of the legacy portion2402 (i.e., due to using half as many tones). In this embodiment, the AP14 (or other suitable receiving device) compensates for the differencein per-tone power before demodulation of the OFDMA data unit 2400, forexample, where L-LTF based channel estimation is used to demodulate anamplitude modulated signal (i.e., a greenfield transmission that omits aHEW-LTF field).

FIG. 26A is a block diagram of an example OFDMA data unit 2600 thatincludes a legacy data unit 2643, according to an embodiment. The OFDMAdata unit 2600 is generally the same as the OFDMA data unit 2200,however the OFDM tone block 2262 corresponds to the legacy OFDM dataunit 2643 instead of the OFDM data unit 2243, in an embodiment. Forclarity, the non-legacy portion 2203 is shown as a single preambleportion. The legacy OFDM data unit 2643 substantially conforms to alegacy communication protocol, such as IEEE 802.11ac, in an embodiment.In some embodiments, the data portion 1616 includes padding OFDM symbolssuch that the legacy OFDM data unit 2643 has a same number of OFDMsymbols as the OFDM data units 2241, 2242, and 2244.

FIG. 26B is a block diagram of an example OFDMA data unit 2650 thatincludes a legacy data unit 2663, according to another embodiment. TheOFDMA data unit 2650 is generally the same as the OFDMA data unit 2200,however the OFDM tone block 2262 corresponds to the legacy OFDM dataunit 2663 instead of the OFDM data unit 2243, in an embodiment. Forclarity, the non-legacy portion 2203 is shown as a single preambleportion. The legacy OFDM data unit 2663 substantially conforms to alegacy communication protocol, such as IEEE 802.11a or IEEE 802.11n, inan embodiment. In some embodiments, the data portion 1616 does notinclude padding OFDM symbols because the legacy communication protocoldoes not support symbol padding.

FIGS. 27A, 27B, 27C, and 27D are example diagrams of short trainingsequences for OFDMA data units, according to various embodiments. In anembodiment, a short training sequence 2701 is a training sequence for aHEW-STF 1610 that spans a 20 MHz sub-band, such as the HEW-STF 1610 ofOFDM data unit 2243. In an embodiment, a HEW-STF 1610 that spans asub-band smaller than 20 MHz, such as the HEW-STFs 1610 corresponding toOFDM tone blocks 2441 and 2442 of FIG. 25A, uses only the correspondingtones of the short training sequence 2701 (i.e., the “upper” tones forthe OFDM tone block 2441 and “lower” tone blocks for OFDM tone block2442). In an embodiment, a short training sequence 2702 is a trainingsequence for a HEW-STF 1610 that spans a 40 MHz sub-band, such as theHEW-STF 1610 of OFDM data unit 2244. In an embodiment, a short trainingsequence 2703 is a training sequence for a HEW-STF 1610 that spans an 80MHz sub-band. In an embodiment, a short training sequence 2704 is atraining sequence for a HEW-STF 1610 that spans a 160 MHz sub-band.

FIG. 28 is a flow diagram of an example method 2800 for generating anOFDMA data unit, according to an embodiment. With reference to FIG. 1,the method 2800 is implemented by the network interface 16, in anembodiment. For example, in one such embodiment, the PHY processing unit20 is configured to implement the method 2800. According to anotherembodiment, the MAC processing 18 is also configured to implement atleast a part of the method 2800. With continued reference to FIG. 1, inyet another embodiment, the method 2800 is implemented by the networkinterface 27 (e.g., the PHY processing unit 29 and/or the MAC processingunit 28). In other embodiments, the method 2800 is implemented by othersuitable network interfaces.

At block 2802, a plurality of different orthogonal frequency divisionmultiplex (OFDM) tone blocks for a wireless local area network (WLAN)communication channel are assigned to a plurality of devices including afirst device and second device. In an embodiment, the plurality ofdifferent OFDM tone blocks includes at least a first OFDM tone blockassigned to the first device and a second OFDM tone block assigned tothe second device. The second OFDM tone block is adjacent to the firstOFDM tone block, in an embodiment. The first OFDM tone block and thesecond OFDM tone block together span a bandwidth equal to a smallestchannel bandwidth of a legacy WLAN communication protocol, in anembodiment. As merely an illustrative example, in an embodiment, thefirst OFDM tone block and the second OFDM tone block together span 20MHz. In some embodiments, the WLAN communication channel corresponds tothe communication channels described above with respect to FIG. 7A, 7B,7C, or other suitable communication channels.

At block 2804, an orthogonal frequency division multiple access (OFDMA)data unit is generated for the WLAN communication channel. The OFDMAunit includes a preamble portion and a data portion, the preambleportion having i) at least a legacy portion that spans the entire WLANcommunication channel, ii) a first non-legacy portion that spans thefirst OFDM tone block, and iii) a second non-legacy portion that spansthe second OFDM tone block, in an embodiment. In some embodiments, theOFDMA data unit corresponds to the OFDMA data unit described above withrespect to FIG. 16, 17A, 17B, 20A, 22, 23, 24, 26A, 26B, or othersuitable OFDMA data units.

In an embodiment, generating the OFDMA data unit includes generating i)a first OFDM data unit of the data portion using first data received forthe first device and ii) a second OFDM data unit of the data portionusing second data received for the second device. In this embodiment,generating the OFDMA data unit also includes modulating i) the firstOFDM data unit on tones in the first OFDM tone block and ii) the secondOFDM data unit on tones in the second OFDM tone block. In an embodiment,the first data is independent of the second data.

In an embodiment, modulating the first OFDM data unit and the secondOFDM data unit includes modulating i) the first OFDM data unit on tonesin the first OFDM tone block using a first tone plan and ii) the secondOFDM data unit on tones in the second OFDM tone block using a secondtone plan. In some embodiments, the legacy portion is modulated using alegacy tone plan that is different from at least the first tone plan(e.g., the tone plan 800 of FIG. 8). In an embodiment, one or more ofthe first non-legacy tone plan or the second non-legacy tone plancorresponds to a fast Fourier transform (FFT) width that is less than aFFT width of the WLAN communication channel. In some embodiments,generating the OFDMA data unit for the WLAN communication channelincludes modulating the OFDMA data unit to span an entire bandwidth ofthe WLAN communication channel. In another embodiment, modulating thefirst OFDM data unit and the second OFDM data unit includes modulatingi) the first OFDM data unit using a same bandwidth as the first OFDMtone block with an integer multiple of tones and corresponding reducedtone spacing and ii) the second OFDM data unit using a same bandwidth asthe second OFDM tone block with the integer multiple of tones andcorresponding reduced tone spacing.

In another embodiment, generating the first OFDM data unit and thesecond OFDM data unit includes generating first data tones using thefirst data and first pilot tones for the first OFDM tone block,separately generating second data tones using the second data and secondpilot tones for the second OFDM tone block, and jointly performing aninverse fast Fourier transform (IFFT) on the first data tones, the firstpilot tones, the second data tones, and the second pilot tones.

In yet another embodiment, generating the first OFDM data unit and thesecond OFDM data unit includes generating the second OFDM data unit toinclude at least one padding OFDM symbol such that the first OFDM dataunit and the second OFDM data unit have a same number of OFDM symbols.In an embodiment, a number of padding OFDM symbols to be included in thesecond OFDM data unit is determined as a difference between a totalnumber of OFDM symbols of the first OFDM data unit and a total number ofOFDM symbols of the second OFDM data unit.

In an embodiment, generating the first OFDM data unit and the secondOFDM data unit includes generating the second OFDM data unit to includeat least one padding OFDM symbol such that a sum of a number of OFDMsymbols in the first non-legacy portion and a number of OFDM symbols ofthe first OFDM data unit is equal to a sum of a number of OFDM symbolsof the second non-legacy portion and a number of OFDM symbols of thesecond OFDM data unit.

In an embodiment, the first non-legacy portion and the second non-legacyportion comprise non-legacy signal fields having respective groupidentifier (ID) sub-fields that indicate whether the corresponding OFDMdata units are any of i) a single user data unit, ii) a multi-usermultiple-input multiple-output data unit to be decoded by an indicateddevice of the plurality of devices, or iii) a portion of the OFDMA dataunit to be decoded by an indicated device of the plurality of devices.

In another embodiment, the first non-legacy portion and the secondnon-legacy portion include non-legacy signal fields having respectivetone block allocation identifiers that indicate the assignment of thefirst OFDM tone block to the first device and the assignment of thesecond OFDM tone block to the second device.

FIG. 29 is a flow diagram of an example method 2900 for generating anOFDMA data unit, according to another embodiment. With reference to FIG.1, the method 2900 is implemented by the network interface 16, in anembodiment. For example, in one such embodiment, the PHY processing unit20 is configured to implement the method 2900. According to anotherembodiment, the MAC processing 18 is also configured to implement atleast a part of the method 2900. With continued reference to FIG. 1, inyet another embodiment, the method 2900 is implemented by the networkinterface 27 (e.g., the PHY processing unit 29 and/or the MAC processingunit 28). In other embodiments, the method 2900 is implemented by othersuitable network interfaces.

At block 2902, a plurality of different orthogonal frequency divisionmultiplex (OFDM) tone blocks for a wireless local area network (WLAN)communication channel are assigned to a plurality of devices including afirst device and second device, in an embodiment. The plurality ofdifferent OFDM tone blocks includes at least a first OFDM tone block anda second OFDM tone block assigned to the first device and a third OFDMtone block assigned to the second device, in an embodiment. The firstOFDM tone block and the second OFDM tone block are separated infrequency by at least the third OFDM tone block. In some embodiments,the WLAN communication channel corresponds to the communication channelsdescribed above with respect to FIG. 7A, 7B, 7C, or other suitablecommunication channels.

At block 2904, an orthogonal frequency division multiple access (OFDMA)data unit is generated for the WLAN communication channel. The OFDMAunit includes a preamble portion and a data portion. In an embodiment,the preamble portion includes at least i) a first legacy portion thatcorresponds to at least the first OFDM tone block, ii) a second legacyportion that corresponds to the second OFDM tone block, iii) a firstnon-legacy portion that corresponds to the first OFDM tone block, iv) asecond non-legacy portion that corresponds to the second OFDM toneblock, and v) a third non-legacy portion that corresponds to the thirdOFDM tone block. In this embodiment, the first legacy portion ismodulated on at least the first OFDM tone block, the first non-legacyportion is modulated on the first OFDM tone block, the second legacyportion is modulated on at least the second OFDM tone block, the secondnon-legacy portion is modulated on the second OFDM tone block, and thethird non-legacy portion is modulated on the third OFDM tone block. Insome embodiments, the OFDMA data unit corresponds to the OFDMA data unitdescribed above with respect to FIG. 16, 17A, 17B, 20A, 22, 23, 24, 26A,26B, or other suitable OFDMA data units.

In an embodiment, the first OFDM tone block and the third OFDM toneblock together span a bandwidth equal to a smallest channel bandwidth ofa legacy WLAN communication protocol. In another embodiment, the firstlegacy portion is modulated on a legacy tone block corresponding to asmallest channel bandwidth of a legacy WLAN communication protocol. Inthis embodiment, the legacy tone block i) overlaps in frequency with thefirst OFDM tone block and ii) has a bandwidth larger than a bandwidth ofthe first OFDM tone block. In a further embodiment, the legacy toneblock includes the first OFDM tone block assigned to the first deviceand the third OFDM tone block assigned to the second device. In thisembodiment, the first legacy portion is modulated on at least the firstOFDM tone block and the third OFDM tone block. In a further embodiment,the data portion includes a first OFDM data unit, for the first device,modulated on the first OFDM tone block and a second OFDM data unit, forthe second device, modulated on the third OFDM tone block. In thisembodiment, at least one of the first OFDM data unit and the second OFDMdata unit includes padding such that a total length of the firstnon-legacy portion and the first OFDM data unit is equal to a totallength of the third non-legacy portion and the second OFDM data unit.

In another embodiment, the data portion includes a first OFDM data unit,for the first device, modulated on the first OFDM tone block and asecond OFDM data unit, for the first device, modulated on the secondOFDM tone block. In this embodiment, the first legacy portion and thesecond legacy portion comprise legacy signal fields that indicate a sametotal duration for i) the first non-legacy portion and the first OFDMdata unit and ii) the second non-legacy portion and the second OFDM dataunit.

In yet another embodiment, the first OFDM tone block and the second OFDMtone block use a same modulation and coding scheme. In an embodiment,the first OFDM tone block uses a modulation and coding scheme (MCS)different from the second OFDM tone block. In a further embodiment, thefirst OFDM tone block and the second OFDM tone block use a same numberof space-time streams. In another embodiment, the first OFDM tone blockand the second OFDM tone block use different numbers of space-timestreams.

In an embodiment, generating the OFDMA data unit for the WLANcommunication channel includes encoding first data for the first OFDMtone block separately from second data for the second OFDM tone block.In another embodiment, generating the OFDMA data unit for the WLANcommunication channel includes encoding and interleaving first data forthe first OFDM tone block together with second data for the second OFDMtone block.

FIG. 30 is a flow diagram of an example method 3000 for generating anOFDMA data unit, according to an embodiment. With reference to FIG. 1,the method 3000 is implemented by the network interface 16, in anembodiment. For example, in one such embodiment, the PHY processing unit20 is configured to implement the method 3000. According to anotherembodiment, the MAC processing 18 is also configured to implement atleast a part of the method 3000. With continued reference to FIG. 1, inyet another embodiment, the method 3000 is implemented by the networkinterface 27 (e.g., the PHY processing unit 29 and/or the MAC processingunit 28). In other embodiments, the method 3000 is implemented by othersuitable network interfaces.

At block 3002, a plurality of different orthogonal frequency divisionmultiplex (OFDM) frequency sub-bands for a wireless local area network(WLAN) communication channel are assigned to a plurality of devicesincluding a first device and second device. The plurality of differentOFDM frequency sub-bands includes at least a first OFDM frequencysub-band assigned to the first device and a second OFDM frequencysub-band assigned to the second device. In some embodiments, the WLANcommunication channel corresponds to the communication channelsdescribed above with respect to FIG. 7A, 7B, 7C, or other suitablecommunication channels.

At block 3004, an orthogonal frequency division multiple access (OFDMA)data unit is generated for the WLAN communication channel. The OFDMAunit including a preamble portion and a data portion, the preambleportion including: a legacy portion that spans the first OFDM frequencysub-band and the second OFDM frequency sub-band using a legacy tonespacing and a legacy tone plan; a first non-legacy portion that spansthe first OFDM frequency sub-band and the second OFDM frequency sub-bandusing the legacy tone spacing and the legacy tone plan; a secondnon-legacy portion that spans the first OFDM frequency sub-band using anon-legacy tone spacing and a non-legacy tone plan; and a thirdnon-legacy portion that spans the second OFDM frequency sub-band usingthe non-legacy tone spacing and the non-legacy tone plan. In someembodiments, the OFDMA data unit corresponds to the OFDMA data unitdescribed above with respect to FIGS. 16, 17A, 17B, 20A, 22, 23, 24,26A, 26B, or other suitable OFDMA data units. In some embodiments, thelegacy tone spacing is an integer multiple of the non-legacy tonespacing.

In an embodiment, generating the OFDMA data unit for the WLANcommunication channel includes generating i) a first OFDM data unit ofthe data portion using first data received for the first device and ii)a second OFDM data unit of the data portion using second data receivedfor the second device, wherein the first data is independent of thesecond data. In this embodiment, generating the OFDMA data unit furtherincludes modulating i) the first OFDM data unit using the non-legacytone plan of the first OFDM frequency sub-band and ii) the second OFDMdata unit using the non-legacy tone plan of the second OFDM frequencysub-band.

FIG. 31 is a flow diagram of an example method 3100 for generating aportion of an OFDMA data unit, according to an embodiment. Withreference to FIG. 1, the method 3100 is implemented by the networkinterface 16, in an embodiment. For example, in one such embodiment, thePHY processing unit 20 is configured to implement the method 3100.According to another embodiment, the MAC processing 18 is alsoconfigured to implement at least a part of the method 3100. Withcontinued reference to FIG. 1, in yet another embodiment, the method3100 is implemented by the network interface 27 (e.g., the PHYprocessing unit 29 and/or the MAC processing unit 28). In otherembodiments, the method 3100 is implemented by other suitable networkinterfaces.

At block 3102, an assignment of a first orthogonal frequency divisionmultiplex (OFDM) tone block within a wireless local area network (WLAN)communication channel is determined. The first OFDM tone block has abandwidth that is less than a smallest bandwidth of a legacy WLANcommunication protocol, in an embodiment. In some embodiments, the WLANcommunication channel corresponds to the communication channelsdescribed above with respect to FIG. 9A, 9B, or other suitablecommunication channels.

At block 3104, a first communication device generates a first portion ofan orthogonal frequency division multiple access (OFDMA) data unit fortransmission on the WLAN communication channel using data tones andpilot tones within the first OFDM tone block. In some embodiments, theportion of the OFDMA data unit corresponds to the portion of the OFDMAdata unit described above with respect to FIG. 24, 25A, 25B, or anothersuitable OFDMA data unit.

In an embodiment, generating the first portion of the OFDMA data unitincludes performing an inverse fast Fourier transform (IFFT) for thefirst portion of the OFDMA data unit with an FFT size equal to the firstOFDM tone block.

In another embodiment, generating the first portion of the OFDMA dataunit includes performing an IFFT for the first portion of the OFDMA dataunit with an FFT size equal to the WLAN communication channel using zerovalues for data tones and pilot tones that are not within the first OFDMtone block.

In an embodiment, the first communication device transmits the firstportion of the OFDMA data unit on the WLAN communication channelconcurrently with a transmission of a second portion of the OFDMA dataunit on the WLAN communication channel by a second communication device.In this embodiment, the second portion of the OFDMA data unit spans asecond OFDM tone block within the WLAN communication channel. In afurther example, the first communication device transmits a legacyportion of a preamble portion of the OFDMA data unit using the firstOFDM tone block and the second OFDM tone block, concurrently with atransmission of the legacy portion of the preamble portion by the secondcommunication device that uses the first OFDM tone block and the secondOFDM tone block.

In an embodiment, transmitting the first portion of the OFDMA data unitincludes transmitting, by the first communication device, a first OFDMdata unit using only the first OFDM tone block, concurrently with atransmission of a second OFDM data unit using only the second OFDM toneblock by the second communication device. In some embodiments, thelegacy portion and the first OFDM data unit are transmitted by the firstcommunication device with a same total power. In other embodiments, thelegacy portion and the first OFDM data unit are transmitted by the firstcommunication device with a same per-tone power.

FIG. 32 is a flow diagram of an example method 3200 for generating aportion of an OFDMA data unit, according to another embodiment. Withreference to FIG. 1, the method 3200 is implemented by the networkinterface 16, in an embodiment. For example, in one such embodiment, thePHY processing unit 20 is configured to implement the method 3200.According to another embodiment, the MAC processing 18 is alsoconfigured to implement at least a part of the method 3200. Withcontinued reference to FIG. 1, in yet another embodiment, the method3200 is implemented by the network interface 27 (e.g., the PHYprocessing unit 29 and/or the MAC processing unit 28). In otherembodiments, the method 3200 is implemented by other suitable networkinterfaces.

At block 3202, an assignment of a first orthogonal frequency divisionmultiplex (OFDM) tone block and a second OFDM tone block for a wirelesslocal area network (WLAN) communication channel is determined. The firstOFDM tone block corresponds to a first fast Fourier transform (FFT) sizethat is less than an FFT size corresponding to the WLAN communicationchannel, the second OFDM tone block corresponds to a second FFT sizethat is less than the FFT size corresponding to the WLAN communicationchannel, and the first OFDM tone block and the second OFDM tone blockare separated in frequency by at least a third OFDM tone block, in anembodiment. In some embodiments, the WLAN communication channelcorresponds to the communication channels described above with respectto FIG. 14A, 14B, or other suitable communication channels.

At block 3204, a first communication device generates a portion of anorthogonal frequency division multiple access (OFDMA) data unit fortransmission on the WLAN communication channel using data tones andpilot tones within the first OFDM tone block and the second OFDM toneblock. In some embodiments, the portion of the OFDMA data unitcorresponds to the portion of the OFDMA data unit described above withrespect to FIG. 24, 25A, 25B, or another suitable OFDMA data unit.

In an embodiment, generating the portion of the OFDMA data unit includesperforming i) an inverse fast Fourier transform (IFFT) for a first OFDMdata unit of the OFDMA data unit with the first FFT size and ii) an IFFTfor a second OFDM data unit of the OFDMA data unit with the second FFTsize. In this embodiment, generating the portion of the OFDMA data unitfurther includes filtering and transmitting the first OFDM data unit andthe second OFDM data unit from separate radio transmitters of the firstcommunication device.

In another embodiment, generating the portion of the OFDMA data unitincludes: performing i) an inverse fast Fourier transform (IFFT) for afirst OFDM data unit of the OFDMA data unit with an IFFT sizecorresponding to the first FFT size and ii) an IFFT for a second OFDMdata unit of the OFDMA data unit with an IFFT size corresponding to thesecond FFT size; filtering and shifting the first OFDM data unit and thesecond OFDM data unit; and combining and transmitting the first OFDMdata unit and the second OFDM data unit.

In an embodiment, generating the portion of the OFDMA data unit includesperforming an IFFT for the portion of the OFDMA data unit with an FFTsize corresponding to the WLAN communication channel using zero valuesfor data tones and pilot tones that are not within the first OFDM toneblock or the second OFDM tone block.

In some embodiments, the first communication device transmits theportion of the OFDMA data unit on the WLAN communication channelconcurrently with a transmission of another portion of OFDMA data uniton the WLAN communication channel by a second communication device. Inone such embodiment, the other portion of the OFDMA data unit spans thethird OFDM tone block of the WLAN communication channel.

Further aspects of the present invention relate to one or more of thefollowing clauses.

In an embodiment, a method includes assigning a plurality of differentorthogonal frequency division multiplex (OFDM) tone blocks for awireless local area network (WLAN) communication channel to a pluralityof devices including a first device and second device, wherein theplurality of different OFDM tone blocks includes at least a first OFDMtone block assigned to the first device and a second OFDM tone blockassigned to the second device, and the first OFDM tone block and thesecond OFDM tone block together span a bandwidth equal to a smallestchannel bandwidth of a legacy WLAN communication protocol. The methodfurther includes generating an orthogonal frequency division multipleaccess (OFDMA) data unit for the WLAN communication channel, the OFDMAunit including a preamble portion and a data portion, the preambleportion having i) at least a legacy portion that spans the entire WLANcommunication channel, ii) a first non-legacy portion that spans thefirst OFDM tone block, and iii) a second non-legacy portion that spansthe second OFDM tone block.

In other embodiments, the method includes any suitable combination ofone or more of the following features.

Generating the OFDMA data unit for the WLAN communication channelincludes: generating i) a first OFDM data unit of the data portion usingfirst data received for the first device and ii) a second OFDM data unitof the data portion using second data received for the second device,wherein the first data is independent of the second data; and modulatingi) the first OFDM data unit on tones in the first OFDM tone block andii) the second OFDM data unit on tones in the second OFDM tone block.

Generating the OFDMA data unit for the WLAN communication channelincludes modulating the OFDMA data unit to span an entire bandwidth ofthe WLAN communication channel.

Modulating the first OFDM data unit and the second OFDM data unitincludes modulating i) the first OFDM data unit on tones in the firstOFDM tone block using a first tone plan and ii) the second OFDM dataunit on tones in the second OFDM tone block using a second tone plan,wherein the legacy portion is modulated using a legacy tone plan that isdifferent from at least the first tone plan.

In some embodiments, one or more of the first non-legacy tone plan orthe second non-legacy tone plan corresponds to a fast Fourier transform(FFT) width that is less than a FFT width of the WLAN communicationchannel.

Generating the first OFDM data unit and the second OFDM data unitincludes: generating first data tones using the first data and firstpilot tones for the first OFDM tone block; separately generating seconddata tones using the second data and second pilot tones for the secondOFDM tone block; jointly performing an inverse fast Fourier transform(IFFT) on the first data tones, the first pilot tones, the second datatones, and the second pilot tones.

Generating the first OFDM data unit and the second OFDM data unitincludes: generating the second OFDM data unit to include at least onepadding OFDM symbol such that the first OFDM data unit and the secondOFDM data unit have a same number of OFDM symbols.

The method further includes determining a number of padding OFDM symbolsto be included in the second OFDM data unit as a difference between atotal number of OFDM symbols of the first OFDM data unit and a totalnumber of OFDM symbols of the second OFDM data unit.

Generating the first OFDM data unit and the second OFDM data unitincludes generating the second OFDM data unit to include at least onepadding OFDM symbol such that a sum of a number of OFDM symbols in thefirst non-legacy portion and a number of OFDM symbols of the first OFDMdata unit is equal to a sum of a number of OFDM symbols of the secondnon-legacy portion and a number of OFDM symbols of the second OFDM dataunit.

In some embodiments, the first non-legacy portion and the secondnon-legacy portion include non-legacy signal fields having respectivegroup identifier (ID) sub-fields that indicate whether the correspondingOFDM data units are any of i) a single user data unit, ii) a multi-usermultiple-input multiple-output data unit to be decoded by an indicateddevice of the plurality of devices, or iii) a portion of the OFDMA dataunit to be decoded by an indicated device of the plurality of devices.

In some embodiments, the first non-legacy portion and the secondnon-legacy portion include non-legacy signal fields having respectivetone block allocation identifiers that indicate the assignment of thefirst OFDM tone block to the first device and the assignment of thesecond OFDM tone block to the second device.

Modulating the first OFDM data unit and the second OFDM data unitincludes modulating i) the first OFDM data unit using a same bandwidthas the first OFDM tone block with an integer multiple of tones andcorresponding reduced tone spacing and ii) the second OFDM data unitusing a same bandwidth as the second OFDM tone block with the integermultiple of tones and corresponding reduced tone spacing.

In another embodiment, an apparatus includes a network interface devicehaving one or more integrated circuits configured to: assign a pluralityof different orthogonal frequency division multiplex (OFDM) tone blocksfor a wireless local area network (WLAN) communication channel to aplurality of devices including a first device and second device, whereinthe plurality of different OFDM tone blocks includes at least a firstOFDM tone block assigned to the first device and a second OFDM toneblock assigned to the second device, and the first OFDM tone block andthe second OFDM tone block together span a bandwidth equal to a smallestchannel bandwidth of a legacy WLAN communication protocol; and whereinthe one or more integrated circuits are further configured to generatean orthogonal frequency division multiple access (OFDMA) data unit forthe WLAN communication channel, the OFDMA unit including a preambleportion and a data portion, the preamble portion having i) at least alegacy portion that spans the entire WLAN communication channel, ii) afirst non-legacy portion that spans the first OFDM tone block, and iii)a second non-legacy portion that spans the second OFDM tone block.

In other embodiments, the apparatus includes any suitable combination ofone or more of the following features.

The one or more integrated circuits are configured to: generate i) afirst OFDM data unit of the data portion using first data received forthe first device and ii) a second OFDM data unit of the data portionusing second data received for the second device, wherein the first datais independent of the second data, and modulate i) the first OFDM dataunit on tones in the first OFDM tone block and ii) the second OFDM dataunit on tones in the second OFDM tone block.

The OFDMA data unit spans an entire bandwidth of the WLAN communicationchannel.

The one or more integrated circuits are configured to modulate i) thefirst OFDM data unit on tones in the first OFDM tone block using a firsttone plan and ii) the second OFDM data unit on tones in the second OFDMtone block using a second tone plan, wherein the legacy portion ismodulated using a legacy tone plan that is different from at least thefirst tone plan.

One or more of the first non-legacy tone plan or the second non-legacytone plan corresponds to a fast Fourier transform (FFT) width that isless than a FFT width of the WLAN communication channel.

The one or more integrated circuits are configured to: generate firstdata tones using the first data and first pilot tones for the first OFDMtone block, separately generate second data tones using the second dataand second pilot tones for the second OFDM tone block, and jointlyperform an inverse fast Fourier transform (IFFT) on the first datatones, the first pilot tones, the second data tones, and the secondpilot tones.

The one or more integrated circuits are configured to generate thesecond OFDM data unit to include at least one padding OFDM symbol suchthat the first OFDM data unit and the second OFDM data unit have a samenumber of OFDM symbols.

The first non-legacy portion and the second non-legacy portion includenon-legacy signal fields having respective group identifier (ID)sub-fields that indicate whether the corresponding OFDM data units areany of i) a single user data unit, ii) a multi-user multiple-inputmultiple-output data unit to be decoded by an indicated device of theplurality of devices, or iii) a portion of the OFDMA data unit to bedecoded by an indicated device of the plurality of devices.

In an embodiment, a method includes: determining an assignment of afirst orthogonal frequency division multiplex (OFDM) tone block within awireless local area network (WLAN) communication channel, wherein abandwidth of the first OFDM tone block is less than a smallest bandwidthof a legacy WLAN communication protocol; generating, at a firstcommunication device, a first portion of an orthogonal frequencydivision multiple access (OFDMA) data unit for transmission on the WLANcommunication channel using data tones and pilot tones within the firstOFDM tone block.

In other embodiments, the method includes any suitable combination ofone or more of the following features.

Generating the first portion of the OFDMA data unit includes performingan inverse fast Fourier transform (IFFT) for the first portion of theOFDMA data unit with an FFT size equal to the first OFDM tone block.

Generating the first portion of the OFDMA data unit includes performingan IFFT for the first portion of the OFDMA data unit with an FFT sizeequal to the WLAN communication channel using zero values for data tonesand pilot tones that are not within the first OFDM tone block.

The method further includes transmitting, by the first communicationdevice, the first portion of the OFDMA data unit on the WLANcommunication channel concurrently with a transmission of a secondportion of the OFDMA data unit on the WLAN communication channel by asecond communication device, wherein the second portion of the OFDMAdata unit spans a second OFDM tone block within the WLAN communicationchannel.

The method further includes transmitting, by the first communicationdevice, a legacy portion of a preamble portion of the OFDMA data unitusing the first OFDM tone block and the second OFDM tone block,concurrently with a transmission of the legacy portion of the preambleportion by the second communication device that uses the first OFDM toneblock and the second OFDM tone block.

Transmitting the first portion of the OFDMA data unit includestransmitting, by the first communication device, a first OFDM data unitusing only the first OFDM tone block, concurrently with a transmissionof a second OFDM data unit using only the second OFDM tone block by thesecond communication device.

The legacy portion and the first OFDM data unit are transmitted by thefirst communication device with a same total power.

The legacy portion and the first OFDM data unit are transmitted by thefirst communication device with a same per-tone power.

In yet another embodiment, a first communication device includes anetwork interface device having one or more integrated circuitsconfigured to: determine an assignment of a first orthogonal frequencydivision multiplex (OFDM) tone block within a wireless local areanetwork (WLAN) communication channel, wherein a bandwidth of the firstOFDM tone block is less than a smallest bandwidth of a legacy WLANcommunication protocol; wherein the one or more integrated circuits arefurther configured to generate, at a first communication device, a firstportion of an orthogonal frequency division multiple access (OFDMA) dataunit for transmission on the WLAN communication channel using data tonesand pilot tones within the first OFDM tone block.

In other embodiments, the device includes any suitable combination ofone or more of the following features.

The one or more integrated circuits are configured to generate the firstportion of the OFDMA data unit includes performing an inverse fastFourier transform (IFFT) for the first portion of the OFDMA data unitwith an FFT size equal to the first OFDM tone block.

The one or more integrated circuits are configured to generate the firstportion of the OFDMA data unit includes performing an IFFT for the firstportion of the OFDMA data unit with an FFT size equal to the WLANcommunication channel using zero values for data tones and pilot tonesthat are not within the first OFDM tone block.

The one or more integrated circuits are configured to transmit, by thefirst communication device, the first portion of the OFDMA data unit onthe WLAN communication channel concurrently with a transmission of asecond portion of the OFDMA data unit on the WLAN communication channelby a second communication device, wherein the second portion of theOFDMA data unit spans a second OFDM tone block within the WLANcommunication channel.

The one or more integrated circuits are configured to transmit a legacyportion of a preamble portion of the OFDMA data unit using the firstOFDM tone block and the second OFDM tone block, concurrently with atransmission of the legacy portion of the preamble portion by the secondcommunication device that uses the first OFDM tone block and the secondOFDM tone block.

In an embodiment, a method includes: assigning a plurality of differentorthogonal frequency division multiplex (OFDM) tone blocks for awireless local area network (WLAN) communication channel to a pluralityof devices including a first device and second device, wherein theplurality of different OFDM tone blocks includes at least a first OFDMtone block and a second OFDM tone block assigned to the first device anda third OFDM tone block assigned to the second device, wherein the firstOFDM tone block and the second OFDM tone block are separated infrequency by at least the third OFDM tone block; and generating anorthogonal frequency division multiple access (OFDMA) data unit for theWLAN communication channel, the OFDMA unit including a preamble portionand a data portion, the preamble portion having at least i) a firstlegacy portion that corresponds to at least the first OFDM tone block,ii) a second legacy portion that corresponds to the second OFDM toneblock, iii) a first non-legacy portion that corresponds to the firstOFDM tone block, iv) a second non-legacy portion that corresponds to thesecond OFDM tone block, and v) a third non-legacy portion thatcorresponds to the third OFDM tone block, wherein the first legacyportion is modulated on at least the first OFDM tone block, the firstnon-legacy portion is modulated on the first OFDM tone block, the secondlegacy portion is modulated on at least the second OFDM tone block, thesecond non-legacy portion is modulated on the second OFDM tone block,and the third non-legacy portion is modulated on the third OFDM toneblock.

In other embodiments, the method includes any suitable combination ofone or more of the following features.

The first OFDM tone block and the third OFDM tone block together span abandwidth equal to a smallest channel bandwidth of a legacy WLANcommunication protocol.

The first legacy portion is modulated on a legacy tone blockcorresponding to a smallest channel bandwidth of a legacy WLANcommunication protocol, wherein the legacy tone block i) overlaps infrequency with the first OFDM tone block and ii) has a bandwidth largerthan a bandwidth of the first OFDM tone block.

The legacy tone block includes the first OFDM tone block assigned to thefirst device and the third OFDM tone block assigned to the seconddevice, wherein the first legacy portion is modulated on at least thefirst OFDM tone block and the third OFDM tone block.

The data portion includes a first OFDM data unit, for the first device,modulated on the first OFDM tone block and a second OFDM data unit, forthe second device, modulated on the third OFDM tone block; wherein atleast one of the first OFDM data unit and the second OFDM data unitincludes padding such that a total length of the first non-legacyportion and the first OFDM data unit is equal to a total length of thethird non-legacy portion and the second OFDM data unit.

The data portion includes a first OFDM data unit, for the first device,modulated on the first OFDM tone block and a second OFDM data unit, forthe first device, modulated on the second OFDM tone block; wherein thefirst legacy portion and the second legacy portion include legacy signalfields that indicate a same total duration for i) the first non-legacyportion and the first OFDM data unit and ii) the second non-legacyportion and the second OFDM data unit.

The first OFDM tone block and the second OFDM tone block use a samemodulation and coding scheme.

The first OFDM tone block uses a modulation and coding scheme (MCS)different from the second OFDM tone block.

The first OFDM tone block and the second OFDM tone block use a samenumber of space-time streams.

The first OFDM tone block and the second OFDM tone block use differentnumbers of space-time streams.

Generating the OFDMA data unit for the WLAN communication channelincludes encoding first data for the first OFDM tone block separatelyfrom second data for the second OFDM tone block.

Generating the OFDMA data unit for the WLAN communication channelincludes encoding and interleaving first data for the first OFDM toneblock together with second data for the second OFDM tone block.

In another embodiment, an apparatus includes a network interface devicehaving one or more integrated circuits configured to: assign a pluralityof different orthogonal frequency division multiplex (OFDM) tone blocksfor a wireless local area network (WLAN) communication channel to aplurality of devices including a first device and second device, whereinthe plurality of different OFDM tone blocks includes at least a firstOFDM tone block and a second OFDM tone block assigned to the firstdevice and a third OFDM tone block assigned to the second device,wherein the first OFDM tone block and the second OFDM tone block areseparated in frequency by at least the third OFDM tone block, andgenerate an orthogonal frequency division multiple access (OFDMA) dataunit for the WLAN communication channel, the OFDMA unit including apreamble portion and a data portion, the preamble portion having atleast i) a first legacy portion that corresponds to at least the firstOFDM tone block, ii) a second legacy portion that corresponds to thesecond OFDM tone block, iii) a first non-legacy portion that correspondsto the first OFDM tone block, iv) a second non-legacy portion thatcorresponds to the second OFDM tone block, and v) a third non-legacyportion that corresponds to the third OFDM tone block, wherein the firstlegacy portion is modulated on at least the first OFDM tone block, thefirst non-legacy portion is modulated on the first OFDM tone block, thesecond legacy portion is modulated on at least the second OFDM toneblock, the second non-legacy portion is modulated on the second OFDMtone block, and the third non-legacy portion is modulated on the thirdOFDM tone block.

In other embodiments, the device includes any suitable combination ofone or more of the following features.

The first OFDM tone block and the third OFDM tone block together span abandwidth equal to a smallest channel bandwidth of a legacy WLANcommunication protocol.

The first legacy portion is modulated on a legacy tone blockcorresponding to a smallest channel bandwidth of a legacy WLANcommunication protocol, wherein the legacy tone block i) overlaps infrequency with the first OFDM tone block and ii) has a bandwidth largerthan a bandwidth of the first OFDM tone block.

The legacy tone block includes the first OFDM tone block assigned to thefirst device and the third OFDM tone block assigned to the seconddevice, wherein the first legacy portion is modulated on at least thefirst OFDM tone block and the third OFDM tone block.

The data portion includes a first OFDM data unit, for the first device,modulated on the first OFDM tone block and a second OFDM data unit, forthe second device, modulated on the third OFDM tone block; and at leastone of the first OFDM data unit and the second OFDM data unit includespadding such that a total length of the first non-legacy portion and thefirst OFDM data unit is equal to a total length of the third non-legacyportion and the second OFDM data unit.

The one or more integrated circuits are configured to encode first datafor the first OFDM tone block separately from second data for the secondOFDM tone block.

In an embodiment, a method includes: determining an assignment of afirst orthogonal frequency division multiplex (OFDM) tone block and asecond OFDM tone block for a wireless local area network (WLAN)communication channel, wherein the first OFDM tone block corresponds toa first fast Fourier transform (FFT) size that is less than an FFT sizecorresponding to the WLAN communication channel, the second OFDM toneblock corresponds to a second FFT size that is less than the FFT sizecorresponding to the WLAN communication channel, and the first OFDM toneblock and the second OFDM tone block are separated in frequency by atleast a third OFDM tone block; and generating, at a first communicationdevice, a portion of an orthogonal frequency division multiple access(OFDMA) data unit for transmission on the WLAN communication channelusing data tones and pilot tones within the first OFDM tone block andthe second OFDM tone block.

In other embodiments, the method includes any suitable combination ofone or more of the following features.

Generating the portion of the OFDMA data unit includes performing i) aninverse fast Fourier transform (IFFT) for a first OFDM data unit of theOFDMA data unit with the first FFT size and ii) an IFFT for a secondOFDM data unit of the OFDMA data unit with the second FFT size; andfiltering and transmitting the first OFDM data unit and the second OFDMdata unit from separate radio transmitters of the first communicationdevice.

Generating the portion of the OFDMA data unit includes performing i) aninverse fast Fourier transform (IFFT) for a first OFDM data unit of theOFDMA data unit with an IFFT size corresponding to the first FFT sizeand ii) an IFFT for a second OFDM data unit of the OFDMA data unit withan IFFT size corresponding to the second FFT size; filtering andshifting the first OFDM data unit and the second OFDM data unit; andcombining and transmitting the first OFDM data unit and the second OFDMdata unit.

Generating the portion of the OFDMA data unit includes performing anIFFT for the portion of the OFDMA data unit with an FFT sizecorresponding to the WLAN communication channel using zero values fordata tones and pilot tones that are not within the first OFDM tone blockor the second OFDM tone block.

The method further includes transmitting, by the first communicationdevice, the portion of the OFDMA data unit on the WLAN communicationchannel concurrently with a transmission of another portion of OFDMAdata unit on the WLAN communication channel by a second communicationdevice, wherein the other portion of the OFDMA data unit spans the thirdOFDM tone block of the WLAN communication channel.

In an embodiment, a method includes assigning a plurality of differentorthogonal frequency division multiplex (OFDM) frequency sub-bands for awireless local area network (WLAN) communication channel to a pluralityof devices including a first device and second device, wherein theplurality of different OFDM frequency sub-bands includes at least afirst OFDM frequency sub-band assigned to the first device and a secondOFDM frequency sub-band assigned to the second device; and generating anorthogonal frequency division multiple access (OFDMA) data unit for theWLAN communication channel, the OFDMA unit including a preamble portionand a data portion, the preamble portion including a legacy portion thatspans the first OFDM frequency sub-band and the second OFDM frequencysub-band using a legacy tone spacing and a legacy tone plan, a firstnon-legacy portion that spans the first OFDM frequency sub-band and thesecond OFDM frequency sub-band using the legacy tone spacing and thelegacy tone plan, a second non-legacy portion that spans the first OFDMfrequency sub-band using a non-legacy tone spacing and a non-legacy toneplan, and a third non-legacy portion that spans the second OFDMfrequency sub-band using the non-legacy tone spacing and the non-legacytone plan.

In other embodiments, the method includes any suitable combination ofone or more of the following features.

Generating the OFDMA data unit for the WLAN communication channelincludes generating i) a first OFDM data unit of the data portion usingfirst data received for the first device and ii) a second OFDM data unitof the data portion using second data received for the second device,wherein the first data is independent of the second data; modulating i)the first OFDM data unit using the non-legacy tone plan of the firstOFDM frequency sub-band and ii) the second OFDM data unit using thenon-legacy tone plan of the second OFDM frequency sub-band.

The legacy tone spacing is an integer multiple of the non-legacy tonespacing.

In another embodiment, an apparatus includes a network interface devicehaving one or more integrated circuits configured to: assign a pluralityof different orthogonal frequency division multiplex (OFDM) frequencysub-bands for a wireless local area network (WLAN) communication channelto a plurality of devices including a first device and second device,wherein the plurality of different OFDM frequency sub-bands includes atleast a first OFDM frequency sub-band assigned to the first device and asecond OFDM frequency sub-band assigned to the second device, andgenerate an orthogonal frequency division multiple access (OFDMA) dataunit for the WLAN communication channel, the OFDMA unit including apreamble portion and a data portion, the preamble portion including alegacy portion that spans the first OFDM frequency sub-band and thesecond OFDM frequency sub-band using a legacy tone spacing and a legacytone plan, a first non-legacy portion that spans the first OFDMfrequency sub-band and the second OFDM frequency sub-band using thelegacy tone spacing and the legacy tone plan, a second non-legacyportion that spans the first OFDM frequency sub-band using a non-legacytone spacing and a non-legacy tone plan, and a third non-legacy portionthat spans the second OFDM frequency sub-band using the non-legacy tonespacing and the non-legacy tone plan.

In other embodiments, the device includes any suitable combination ofone or more of the following features.

The one or more integrated circuits are configured to: generate i) afirst OFDM data unit of the data portion using first data received forthe first device and ii) a second OFDM data unit of the data portionusing second data received for the second device, wherein the first datais independent of the second data, and modulate i) the first OFDM dataunit using the non-legacy tone plan of the first OFDM frequency sub-bandand ii) the second OFDM data unit using the non-legacy tone plan of thesecond OFDM frequency sub-band.

The legacy tone spacing is an integer multiple of the non-legacy tonespacing.

At least some of the various blocks, operations, and techniquesdescribed above may be implemented utilizing hardware, a processorexecuting firmware instructions, a processor executing softwareinstructions, or any combination thereof. When implemented utilizing aprocessor executing software or firmware instructions, the software orfirmware instructions may be stored in any computer readable memory suchas on a magnetic disk, an optical disk, or other storage medium, in aRAM or ROM or flash memory, processor, hard disk drive, optical diskdrive, tape drive, etc. Likewise, the software or firmware instructionsmay be delivered to a user or a system via any known or desired deliverymethod including, for example, on a computer readable disk or othertransportable computer storage mechanism or via communication media.Communication media typically embodies computer readable instructions,data structures, program modules or other data in a modulated datasignal such as a carrier wave or other transport mechanism. The term“modulated data signal” means a signal that has one or more of itscharacteristics set or changed in such a manner as to encode informationin the signal. By way of example, and not limitation, communicationmedia includes wired media such as a wired network or direct-wiredconnection, and wireless media such as acoustic, radio frequency,infrared and other wireless media. Thus, the software or firmwareinstructions may be delivered to a user or a system via a communicationchannel such as a telephone line, a DSL line, a cable television line, afiber optics line, a wireless communication channel, the Internet, etc.(which are viewed as being the same as or interchangeable with providingsuch software via a transportable storage medium). The software orfirmware instructions may include machine readable instructions that,when executed by the processor, cause the processor to perform variousacts.

When implemented in hardware, the hardware may comprise one or more ofdiscrete components, an integrated circuit, an application-specificintegrated circuit (ASIC), etc.

While the present invention has been described with reference tospecific examples, which are intended to be illustrative only and not tobe limiting of the invention, changes, additions and/or deletions may bemade to the disclosed embodiments without departing from the scope ofthe invention.

What is claimed is:
 1. A method, comprising: assigning a plurality ofdifferent orthogonal frequency division multiplex (OFDM) tone blocks fora wireless local area network (WLAN) communication channel to aplurality of devices including a first device and second device, whereinthe plurality of different OFDM tone blocks includes at least a firstOFDM tone block and a second OFDM tone block assigned to the firstdevice and a third OFDM tone block assigned to the second device,wherein the first OFDM tone block and the second OFDM tone block areseparated in frequency by at least the third OFDM tone block; andgenerating an orthogonal frequency division multiple access (OFDMA) dataunit for the WLAN communication channel, the OFDMA data unit including apreamble portion and a data portion, the preamble portion having atleast i) a first legacy portion that corresponds to at least the firstOFDM tone block, ii) a second legacy portion that corresponds to thesecond OFDM tone block, iii) a first non-legacy portion that correspondsto the first OFDM tone block, iv) a second non-legacy portion thatcorresponds to the second OFDM tone block, and v) a third non-legacyportion that corresponds to the third OFDM tone block, wherein the firstlegacy portion is modulated on at least the first OFDM tone block, thefirst non-legacy portion is modulated on the first OFDM tone block, thesecond legacy portion is modulated on at least the second OFDM toneblock, the second non-legacy portion is modulated on the second OFDMtone block, and the third non-legacy portion is modulated on the thirdOFDM tone block.